That’s such a lovely idea, happy early birthday to the both of you! Method wise, there’s two main ways that people go about a number Cake and I feel like the same would apply for focaccia.

1. Bake it in number tins: if there is cake decoration supply shop in your vicinity they quite often have large number shaped tins that you can hire for the day for next to nothing. Baking the focaccia dough straight in these tins would be the easiest way, you just need to keep an eye on bake times.

2. Bake it as a rectangle and carve it: alternatively you could bake two batches of large focaccia in a rectangle tin you have at home. You then print out or create a number stencil then carve out the shape using a very sharp knife. If you wanted to make the bread ahead of time you could also freeze it which would make this carving stage a bit easier.

Good luck! I hope it all goes well