Camera, chap stick, sharpie (to sign hats), park map, epipen & Benadryl, Tylenol/Advil, wipes in a zip lock bag, phone.
My kids are 14, 11 & 9 and they have gone at ages 15 mo, 22 mo, 2.5 yrs, 4, 4.5, 7, 8, 9, 11 (I think) and I never brought anything for them to do in line. They are good kids when in public and don't run, make a lot of fuss, etc.... There are so many things to look at that there has never been an issue. I used to bring a snack, maybe I did 2 yrs ago too, but I limit my self since we are strollerless now and my kids carried their own crap, aka their water bottles. I think they moaned but they were thankful to take a sip when needed.
And we go to the park early, we do the early entry park and we are there 1/2 hour before opening. We know what ride we want to do and aim for there.