Ungrateful little gits! I only once had a shop bought cake for DD's birthday. She was three and it was an excellent one from M & S. Most parties DD has been to have had those awful supermarket confections with a Barbie/Scooby/Doo/other icing. They always went straight into the bin as DD wouldn't eat them. After the M & S cake I always made birthday cakes and none of DD's friends turned their noses up at them.
I'm sorry to say 7 year old boys are the least pleasant examples of humanity. I've done many parties in my time but the worst by far was DS's 7th. I had a rugby coach do an hour's training, then sat them down outside the rugby club for food. Two little, er, tykes threw balls at the rugby coach's head, stole the figures from the top of the cake before the "happy birthday" and pocketed them, then had a jelly fight, then declared the party "boring" and "the worst party ever". They were not invited to many more parties after that, once word got round!