I'm still pretty new to adventuring myself, but from the little adventure expirience I have, I know what I SHOULD have packed and hopefully this list will help you out.
-Coolant, almost every 4.0 runs hot, especially on the trails.(really good idea to get that taken care of before you hit the trails cause the wife and kids are not going to like having the heater going on a 95 degree day)
-Fuses, simple but you never no when one could blow
-The tools you don't think you will need. For example, hammer, zip ties, air pressure gague, silicone, loctite, jb weld. (I have a buddy with an xj who's engine block was held together for years with jb weld.)
-spare parts, I realize you can't. Bring a spare everything but your going to be pretty upset if you can't get home because of a u joint.
-lastly sunscreen cause if your pasty white like me nothing kills a weekend in the sun like getting burnt on the first day.
I would recommend a roof rack, I love mine. I'll try to post a few picture tomorrow to show you what can be done with a few bucks and a welder.