Shawarma after every weekend match. How often do you let a 12 year old eat out with friends?

Our son plays cricket with the same group of boys most evenings. On weekends, after the longer matches, they've started going to the shawarma place outside the colony. Twice last week, three times the week before. He uses his own pocket money, so it isn't really about cost. It's the frequency, and that dinner at home on those days turns into a negotiation because he's full at 8. I cook most evenings and I'd rather he ate with us. Do you set a number, like once a week, or let the group's habits decide? And if you set one, does it hold when every other boy is going?