Ragwort read my mind.
DH, DS and I are going on a camping holiday for a week and I am planning to spend £250 on all food, drinks and trips (but not including accommodation and petrol).
DS is only a baby so that works out at £17.85 each per day for an adult. I think that's more than enough.
You gave your son an average of £18 for each day, not including food and drinks, which is way too much for an 11 year old.
You really can't complain that over two days (Mon and Tues) he spent £40 in the arcade. So he only went £2 over his daily budget, £4 over for the two days.
I remember going on holiday in my early teens with my grandparents and spending my entire holiday money in the arcade in one night (in one machine)! It was £7 for a week and that was in the 90s.
Putting the maths aside, did you ask the other mother how much pocket money her son would have?
My parents would have been absolutely mortified to take a friend of mine on holiday and see that he/she had £90 to spend for a week. They could in no way have given me that much and would have been massively embarrassed. They would also have been very annoyed to be offered £40 for food by such extravagant parents to then have the same Loadsa Money ask for it back! It would probably have been better not to offer than to ask for it back!
YABU.