Agree with bpounds other than I still carry some obligatory spare parts.
Bottle Jack is great idea, serpentine belt (but today the chance of breaking a serp belt unless there's a failed component that you DONT have with is about zero). Grease gun. Fuel filters (diesel, none needed for gas) and spare trailer bearing set (which should be a zero need with proper maintenance).
I have one trailer with oil bath hubs which will smoke a bearing if a seal goes bad or the cap leaks. Haven't had a bad greasabke bearing since the old days of running X country at 90mph with a little snomobile trailer with those 12" rims.
Add a roll of rebar tie wire and some mule tape to the kit IMO. Those 2 things and duct tape could hold the space shuttle together in a pinch.
More so, if your equipment is well maintained, you'll very likely have zero issues.
Sounds like an awesome trip!!!