Birthday cake suggestions

I'm going to Osaka with my family in March for 4 days and my mom's birthday is 2 days after our trip so I want to do something special for her.

At first I was thinking of a birthday dinner but it might be a little out of budget since there'll be four of us. So, does anyone know of a good bakery that can write "happy birthday" on a slice of cake and if I need to make any reservations?

I'd also be open to any ideas on celebrating her birthday in Osaka!