Soft sponge with butter cream
I did a store bought chocolate cake and my son loved it, I wasn’t too worried about the sugar intake as it was only a one off xx
Either would work honestly, a plain vanilla sponge with cream in the middle could also work but doesn’t look as pretty as a store one x
I know quite a few people who've done them and they just use supermarket cakes :) but you could definitely make a healthy one if you wanted to! I just had a quick look online and there are lots of specific cake smash recipes. I wouldn't worry about the sugar personally, one day won't hurt and they won't eat much of it anyway :)