Most of the time I just use my pick-up for everything. I have a large wood box & moving pads,to hold rockets.
I have another box next to it which holds 3 smaller toolboxes.
1. actual tools. screwdrivers, drill, bits, wrenches,pliers,etc.
2. igniters...dual deploy stuff, nutz, bolts, CA, everything needed for repairs.
3. tracking equipment GPS.
Utilize the tailgate as a table.
Many of my friends do this, saves time setting up & breaking down.
Just bring needed chairs & possible table if ya fill up your ride with too much.
You'll see many SUV's & minivans being used as 'rocket haulers'.
On the other hand, I have gone to launch, with nothing more than 3-4 rockets totally prepped and ready to fly. Bring along some igniters and tracking...that's it.
As for significant other, ask/tell them beforehand what they are in for...show a You Tube video of rockets being launched, you may have one who reacts like a launch is as much fun as watching paint dry......DO NOT take her if that's the attitude, let her go shopping or have a day by herself, while you watch the kids. NOTHING worse than a spouse/girlfriend with the "can we go now"? issues.
Ask what will make them happy, my guess is same type of stuff as going to beach, camping, fair.
Drinks, snacks, a rest room facility [within reasonable driving]...some woman loathe PORTO-POTTIES... better find out all this stuff ahead of time. Sunglasses, headwear, you will be in sun, looking up a great deal of the time, be prepared for sunburn & hydration.
And the real simple answer is: everything you need to fly your rockets! If there is an onsite vendor that helps a lot.