Dividing up money /handing envelopes to each person makes sense IF you're going to be splitting up /going your own ways in the parks, and you might not be eating together.
Our next trip will be a celebration of our retirement, and we're "treating" our adult children (no actual children are going on this trip). We intend to give them each a gift card, which is kinda the modern version of the envelope system.
The card will be enough to pay for two meals a day for each of our planned park days. They can decide how to use it; they can eat snacks all day, or they can eat one big, expensive dinner. We don't have to be together for every meal, and I don't intend to monitor whether they're using their gift cards for real meals or just Dole Whips. With everyone having a gift card, they won't need to feel that they "owe us" a nice dinner or even a snack.
No! Its vacation! If kid wants a $14 milkshake, and doesn't drink it all, I will finish it.
I don't have small children anymore, but -- when I did -- I did balk at $14 milkshakes.
I go through the menus and guess what our food costs will be, then I add on a little more.
Yes, you can hardly go wrong by going over the online menus and projecting your costs -- looking at a menu, I can predict what my family members are likely to order. Do add on a little for tax and tips.
Beyond that I would never allocate my kids (or adults) a 'food allowance' on vacation. Yikes.
Maybe that's what I'm doing by giving my adult children each a gift card, but I'm not feeling "yikes" about it. If they spend all of my money, they'll have to reach into their own pockets, but each of them is capable of doing that.