My boys are 8, 6 & 2 & we always take food with us. I dont mean sandwiches I mean things like fruit, box of pringles & digestive biscuits.
They are really easy snacks to carry around & are also quite handy in some of the longer queues.
We've seen lots of families taking in coolers on wheels (massive to boot) into the parks nothing has ever been stopped so far. They will ask to see the contents of a cooler just in case there's something concealed just like a bag check.
I think maybe it's dawning on them that not all families can afford to eat in the parks some families keep their food in a cooler in the car and pop out at mealtimes to refuel the troops. They will have their hands stamped for readmission.
my in laws take there own food into DW all the time and have never had a problem with it , they find a seating area buy a hot or cold drink from a DW outlet and eat there own food...