Lesson to people on MN, always have a spare cake just in case.
I don't understand the fury at the watermelon, it's done nothing wrong. Also I can't understand with DC would be traumatised not having a cake. They've had a party, got presents, got to play with mates & have party food.
It's really quirky, but most people like cake, not everyone is a fan of water melon.
We've always said to DC, do you want a birthday party, or would you like an extra present to the value of a party. It's usually gone the way of present, then take a couple of friends to the cinema and then Nando's. My children are obsessed with the place, keeping their little flags from food and fighting over who gets DH's super hot (Nando's you lie 
) flag.
We've usually planned like outdoor places that hold parties, or the football centres that do parties. I think with the latter you get the room hire after, but bring own food and cake.
I don't think I'll see 50, apart from my 18th I've never had a party or anything, my 18th I went to a restaurant which was nice.
With ADHD there is a lot of misunderstanding, I'm from the age group where there were no labels, kids were just little shits in their youth. It's horrid to think these kids had issues and were getting caned within an inch of their lives.