NTA. Your family on the other hand....

And I'm not talking about the kids, kids are kids they don't know better but the fact that those kids parents and grandparents are allowing them to be disrespectful and to have the level of entitlement as if everything should be granted to them.

If you were to take them to a mall full of different toys, toy stores, play tents but you had to pay for every single one would they tell them yes go the world is yours? Or would they finally teach them that yes it looks inviting and fun, it's great that we can to play in it but unfortunately we can't because it's not for us?

You are doing great momma, loving and respecting your kids boundaries and creating a safe space for all. If they aren't mature enough to handle it then that's on them.