Spare batteries for the smoke alarm and CO2 detector. Very annoying if they start to beep in the middle of the night because the batteries are dying. Safer to replace them quickly vs. popping batteries out and not using them. A small level is a good if U don't have one on your trailer.
A Gas fire pit. A lot of places have fire bans during the summer so a propane fire pit will keep the kids happy.
Possibly walkie talkies if you won't have cell reception where you camp. If your new to parking a trailer , wife outside with one, you inside the truck with one so you can have her eyes helping you back in.
Enjoy your adventures
2012 Ram1500 Laramie crew cab 5.7 HEMI
2017 Surveyor 245BHS Travel Trailer