There our names that I absolutely love but my partner thinks when they are older they are going to sound really silly… [name_f]Do[/name_f] you think this is a case with some bames? And what names? 
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I love
[name_f]Poppy[/name_f]
[name_f]Hattie[/name_f]
[name_f]Lottie[/name_f]
[name_f]Bambi[/name_f] [name_f]Grace[/name_f] (naughty favourite hehe)
[name_u]Ollie[/name_u]
[name_u]Bobby[/name_u]
But he thinks they dont convey well onto adults? 
I kind of agree with your partner (except on [name_f]Hattie[/name_f]…it has an older, vintage feel to me, so I can rather easily picture it on an adult). The rest of them all are or can be nicknames. It’s kind of not that they would sound silly, it’s more that they don’t age very well, for the most part. Also, just having a nickname as a first name can make situations such as finding a job harder. If you are really attached to these names, and if he has no objections to them, I think using these solely as nicknames would be a great solution. For example:
[name_f]Charlotte[/name_f] “[name_f]Lottie[/name_f]”
[name_m]Oliver[/name_m] “[name_m]Oliver[/name_m]”
[name_m]Robert[/name_m] “[name_u]Bobby[/name_u]”
I’ve heard [name_f]Poppy[/name_f] as first name, so I can’t think of anything it could be short for. I personally don’t care for [name_f]Bambi[/name_f], but [name_f]Grace[/name_f] is nice. [name_f]Gracie[/name_f] could be a nickname option too. I realize that the possible first names I’ve suggested are pretty common and may not be your style but it was just to illustrate some examples
I think [name_f]Poppy[/name_f] can work fine as a first name, I prefer it as a fullname to a nickname. A lot of the time I just think of my Grandparents and their friends named [name_f]Elsie[/name_f], [name_f]Annie[/name_f], [name_f]Hettie[/name_f] etc, if it works for a 80+ year old person why not an adult. I disagree with the previous poster about the job situation I have people at work named Babylyn, [name_f]Honey[/name_f]-[name_u]Lane[/name_u] and [name_f]Libby[/name_f]- they never had trouble getting a job.
If you really are worried about them sounding too like nicknames you can always use them as nicknames.
Chalotte- [name_f]Lottie[/name_f]
[name_f]Harriet[/name_f]- [name_f]Hattie[/name_f]
[name_f]Poppy[/name_f]- [name_f]Penelope[/name_f], [name_f]Olympia[/name_f]
[name_f]Bambi[/name_f]- a little harder to find a first name, maybe [name_f]Grace[/name_f] [name_f]Bambi[/name_f] could work? My bf and his brother both go by middle’s
[name_u]Ollie[/name_u]- [name_m]Oliver[/name_m], [name_f]Olwen[/name_f]
[name_u]Bobby[/name_u]- [name_m]Robert[/name_m]
I have the names [name_u]Sunny[/name_u] and [name_f]Netty[/name_f] on my own list, I have thought about using the name [name_f]Sonnet[/name_f] nn [name_f]Nettie[/name_f], but prefer [name_u]Sunny[/name_u] by itself.
Nothing wrong with nickname names; [name_m]Dave[/name_m], [name_m]Johnny[/name_m], [name_f]Millie[/name_f], [name_f]Tillie[/name_f], …
Many individuals have gone by a nickname name, whether it was their actual full name or a nickname, throughout time. [name_m]Even[/name_m]; Judges, presidents, doctors, lawyers.
I can easily see, and have known or known of, adults with all the names you listed except [name_f]Bambi[/name_f]. Personally I would avoid that one. It does not come across as a nickname name to me, it comes across as more of a, as you say a “naughty” name.
I do kind of agree with your partner on this one. I can’t see [name_f]Bambi[/name_f] [name_f]Grace[/name_f] being taken seriously as an adult. [name_f]Hattie[/name_f] and [name_f]Poppy[/name_f] are actually fine, I think. [name_f]Lottie[/name_f]'s ok as long as it’s a nickname for [name_f]Charlotte[/name_f]. That way, she can choose to go by [name_f]Charlotte[/name_f] in the professional world if she so desires. I think [name_u]Ollie[/name_u], short for [name_m]Oliver[/name_m], would be fine and [name_u]Bobby[/name_u], short for [name_m]Robert[/name_m], also.
Honestly, I think all of the names are fine, except [name_f]Bambi[/name_f] [name_f]Grace[/name_f]. For me it’s too linked to the cartoon to be taken seriously.
As other posters have suggested, you could use them as nick names
I don’t think they age very well, except [name_f]Hattie[/name_f].
Tbh - I know an adult man called [name_u]Robbie[/name_u] and he is made fun of A LOT for it. [name_u]Bobby[/name_u] seems like it might be worse.
However, I don’t think that makes them unusable as nicknames for a child - and for a mom or family to use forever. I have a few family members like that - they still go by a childhood nickname to family or even their wives, but at work and such go by their full name or a more adult nn.
Ex: FIL [name_u]James[/name_u] goes by [name_u]Jamie[/name_u] to his family, but [name_m]Jim[/name_m] at work and to friends. [name_m]Carlton[/name_m] goes by [name_m]Corky[/name_m] to family, but [name_m]Carl[/name_m] professonally. [name_f]Rhiannon[/name_f] goes by [name_f]Annie[/name_f] to family but her full name to friends and at work.
I’d choose names like [name_f]Penelope[/name_f], [name_f]Harriet[/name_f], [name_f]Charlotte[/name_f], [name_m]Oliver[/name_m], and use a nn, or if you don’t like those be more creative!
[name_f]Ava[/name_f] is actually a very common name on older people, so it’s funny you should say that! I think some of that it personal: I can’t picture [name_f]Hannah[/name_f] or [name_f]Chloe[/name_f] on an adult at all, but they’re quite popular given names, so I guess many people can!
The problem with these names is they are all nickname based. They could work well on a kid as a nickname then transfer into formal names for an adult.
[name_f]Poppy[/name_f] - This is the only non-nickname name though I still cant see it well on an adult.
[name_f]Hattie[/name_f] - I guess it could work, but I would say [name_f]Harriett[/name_f] or [name_f]Angharad[/name_f] are better full names.
[name_f]Lottie[/name_f] - Despite what others say I think this one works best on its own. I suppose that might be because I’ve known an adult whose actual name was [name_f]Lottie[/name_f]. But [name_f]Charlotte[/name_f] is pretty so I guess that works too.
[name_f]Bambi[/name_f] [name_f]Grace[/name_f] - this is a no no whatever age. [name_f]Bambi[/name_f] isn’t and shouldn’t be a name, and if you love it that much at least put it in the middle spot.
[name_u]Ollie[/name_u] - this to me appears more feminine, perhaps because of the ie. Like [name_f]Oliana[/name_f] or [name_f]Olivia[/name_f]. [name_u]Olly[/name_u] looks more masculine.
[name_u]Bobby[/name_u] - Hate it, its so boring! [name_m]Robert[/name_m] - and if you absolutely have to call him [name_u]Bobby[/name_u] then whatever.