I personally do not think your need to continue with a vowel name. The theme wasn’t intentional and is quite subtle in my opinion. I wouldn’t have picked up on it, had you not mentioned it in your post.
I love [name_f]Grace[/name_f] or [name_f]Mabel[/name_f] with your three! [name_f]Gracie[/name_f] and Mae/Maisie/Belle/Billie fit in nicely too.
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f], [name_u]Oliver[/name_u] and [name_f]Grace[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f], [name_u]Oliver[/name_u] and [name_f]Mabel[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Gracie[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Mae[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Maisie[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Belle[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_u]Billie[/name_u]
I also quite like [name_f]Emmeline[/name_f] too.
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Emmeline[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Emma[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Emmy[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Millie[/name_f]
[name_u]Eli[/name_u], [name_f]Addie[/name_f], [name_u]Oliver[/name_u] and [name_f]Lina[/name_f]
I do agree with @katinka that [name_f]Eloise[/name_f] is a bit too close to [name_u]Eli[/name_u]. Especially if you consider the nickname [name_f]Ellie[/name_f]. But with the nickname [name_f]Lulu[/name_f], it would be fine.
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Felicity[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_u]Ruby[/name_u]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Audrey[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Pippa[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Philippa[/name_f] “Pippa”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Rosalie[/name_f] “Rosie”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_u]Evelyn[/name_u] “Evie/Evy”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Hannah[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_u]Hazel[/name_u]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Lucy[/name_f] “Lulu”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Imogen[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Beatrix[/name_f] “Bea”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Bea[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Ivy[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Norah[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Eleanor[/name_f] “Nora”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Lydia[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_u]Josie[/name_u]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Josephine[/name_f] “Josie”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Kate[/name_f] “Katie”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Lorelai[/name_f] “Rory”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Lila[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Faith[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Bronte[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Clara[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Thea[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Thalia[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Ava[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Susannah[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Poppy[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Caroline[/name_f] “Carrie”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Isabella[/name_f] “Bella”
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Estella[/name_f]
[name_u]Eli[/name_u], [name_f]Adelaide[/name_f] (Addie), [name_u]Oliver[/name_u] and [name_f]Liana[/name_f]