A few other options -- Society Fair makes a "birthday cake just because" that's a teeny individual size (about 4") and would be great. They could also do a big coordinating cake, I'm sure. It's good, I can vouch for that!
Also, the Swiss Bakery (Braddock and 495) and Alexandria Pastry Cafe (King and 395) both make great cakes we've gotten for our DC's birthday. Lots of flavor choices and nice decoration options beyond Dora the Explorer plastic junk and typical grocery bakery piped flowers (although I think they can do the kiddy decor too if that's what you're looking for

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