For the camper you'll need blocks or similar to level from side to side and some kind of chocking system. THEN level front to back. NOTE: stabilizers only try and prevent movement, they don't hold as much weight as you'd like.
You'll also need a wrench, jack and pump to maintain the air in the trailer tires. Try to keep the tires at max load inflation at all times even in storage. Trailer tires age and rot quickly (on the inside where you can't see it) when not being used, so learn how to read the DOT code to replace them every 5 or 6 years.
Try to keep a set of tools dedicated to the trailer. That way they are always available when needed and less to pack/unpack.
This goes for many other items. Try to keep the trailer stocked with items that are specific for pop up camping - dishes, bedding, other equipment. This minimizes what needs to be loaded or unloaded before or after a trip. Unlike a house, keeping the trailer clean and neat ALL the time is more critical. It's also easier to find things and you reduce attracting undesirables (bugs and animals). Remember that you are now going to where THEY live.
Find a way to keep the battery charged and conditioned. Just because the battery is on a charger, doesn't mean it's not being charged correctly. If it is not a maintenance free battery, then you must also check the water level religiously. Just because the trailer is connected to your vehicle, it's only trickle charged and if the battery has discharged too much while in storage it might not be enough so that you can use it. You'll also need to find out if the popup's converter (when connected to a campground shore power provides 12v and charges the 12v battery) has a smart charger that does not overcharge the battery and conditions it as well. When I had mine, I had an 400 watt inverter installed so if I wasn't on shore power, the battery provided 110v for small items.
When we travelled with our kids when they were that young we left as much electronics at home so that we needed less electricity. For the items you must have (coffee maker, toaster, etc.) know the wattage ratings so that you don't overload your rig's converter system. A popup trailer pretty much uses 15 or 20 amps and that's about it.
After you've loaded it all up, get to some scales and weigh, the vehicle only (while hitched), then both the vehicle and the trailer, then finally just the trailer, and compare these numbers to all the ratings. If any of these are over the weight rating you are considered overweight and could make you liable in an accident regardless of the anticipated fault. This is not as critical with a pop up, but something you should get used to knowing.
Last tip for now. The camper for us was something to sleep in, or dine in especially if the weather was bad. Otherwise plan for most activities to be outdoors especially if the weather is nice. Even though we had a stove and cooler in our unit, we still used our outdoor cooking gear as much as possible. This keeps the popup interior clean and not smelling like food which attracts critters into the rig. It will also last longer and stay looking good and pleasant to sleep in.
If you have any questions about what I've posted please ask. I've hit on a lot of things and some you might not be at all familiar with. Don't be shy about asking.