Op it REALLY depends what you mean by, "plenty of room to carry everything." Myself and many others, enjoy going bag free best of all. And I say this as someone who -over the years- tried a great many bags.
For us, if we have to carry a bag, I try very hard to go as compact as possible. Like, instead of carrying a full bottle of sunscreen- we apply before we leave- then I carry a small chapstick style stick of sunscreen. If I have any bag, I prefer a SMALL crossbody bag with ONE compartment.
Mostly we eliminate anything bulky, and don't miss it. The big exception is a bottle of water, so DH wears cargo shorts. We also request lots of water with each meal.
The other bulky item we sometimes can't eliminate is jackets. We either go with cheap plastic ponchos that fold up in a packet. We also own rain jackets that fold up into their own pocket. Technically the ones we have are windbreakers, not rain wear, but they work. Ours came from LL Bean, but other places carry similar ones.
Last, we no longer carry everything with us all the time. We take a second before we leave the room to eliminate what we don't need, and adopting that policy has been great.
Other than cash and emergency meds, in a pinch, we can get much of what we might need in the parks. If we ever carry food, we consume it within about half an hour.
My last tip - try it out in advance! Whichever bag you choose, make sure it is comfortable on YOU, with the items you plan to carry. Bags with straps that dig into your shoulders, or make your back wet with sweat are no fun.
