The wildlife is a bit of a concern. I don't expect to be attacked every time I go out into the wilderness, but it's better to be prepared, just in case. Consider having bearspray for each member of your party. Also, follow the food storage rules (this includes soaps/shampoos/toiletries).
The cabins at Tower Junction are a nice alternative to camping. Also, the chuck-wagon cowboy dinner ride located at Tower Junction was a great experience.
There are several "general stores" in the park, but depending on where you stay, it might be a significant drive to get to one. There are some services in the "gateway" towns (Gardiner, Cooke City, West Yellowstone, Cody- sort of) but keep in mind that these are very small towns with not a lot in the way of services.
Yellowstone is HUGE. Most people who have never been here have no idea just how big the park is. Just driving through the park from one side to the other takes hours. Just a heads up. When planning your activities, plan to group them together by region. Different regions have different attractions. Also, plan when/where/what you'll eat. Feeling a bit hungry, then realizing it's a two hour drive to any food service, sucks. Even more so to get there and they're closed.
I've not camped in the park, as the way they do it is not really camping to me, too many people.
Things to not miss: Between Mammoth and Gardiner there is a spot in the river (where the Firehole River meets the Gardiner River??) where you can soak in the hot waters. Kind of an outdoor natural hot-tub.
'76 CJ-7, '43 CJ-2a, '78 Bronco,'78 CJ-7, '75 CJ-5, '78 CJ-7, '80 CJ-7, '78 SJ, '79 SJ, '78 and a '76 FJ-40 , '90 XJ, '91 XJ, '86 CJ-7, '95 ZJ, '68 CJ-101 Commando, '00 TJ, '68 M-715, 2 '86 Military Blazers, '96 LR Discovery, '86 CJ-7, '91 YJ, '99 TJ, 07' JKU Rubi, 1988 YJ, 1973 Commando, 3 Diesel Excursions....
Now back to a 2013 JKU Rubicon with "stuff", planning 37's with minimal lift.
I've tried them all... Jeeps are still the best. (0||||0)