I do not think it would be hard at all for a child to handle - certainly not in the age where
Isabella is one of the top names!
Tamsin and even
Tommy are great ideas for short, sassy nicknames.
This is a fave name of mine also. I think it has a great urban flair to it, very prep-school cute.
Thomasina Evelyn is gorgeous. I also like
Thomasina Eva and
Thomasina Eve! Nice picks :D