Personally, I think [name_f]Sunshine[/name_f] would be a more optimal choice, and just call her [name_u]Sunny[/name_u]. A middle name that is a more classic, straightforward one would be a great idea.
Again, many thanks to everyone who has replied!
I really appreciate the reassurance. I can’t seem to get on board with [name_f]Sunshine[/name_f] just yet- I’ve considered it, and it’s definitely something I’ll keep in the back of my mind, because I feel it does have the potential to grow on me.
I think [name_u]Sunny[/name_u] is a sweet name and it’s very usable. It’s not like it’s [name_f]Happy[/name_f] or Pretty (which [name_f]IMO[/name_f] would definitely lead to teasing). I think of the Lemony Snicket series which I read when I was younger.
I think it is totally usable and is a very happy, cheerful name! Sounds like you have put a lot of thought in also and it suits your circumstances well 