Strapping bikes in the back of a pickup is not complex. Use cargo tie-down straps. Cam buckles are best. Ratchet straps are unnecessary and might break stuff. The ones with metal hooks will work. I personally prefer continuous loop straps because they don't have metal hooks to damage anything. For each bike, use a strap over each end of handlebar, hooking or looping around something that won't be damaged (not around soft handgrips, shifter or brake components or cables).
I recently did a trip with two bikes secured this way, and a third on a hitch-mounted rack. There is no reason you can't get more mounted in the truck bed though. You can mount two, parallel, facing foward, and two parallel facing the rear.
Some people prefer tailgate blankets. I'm not sure why. My neighbor uses one.
These same methods will work with a trailer, and if you're outfitting something for more than one use, you can add bike wheel-chocks hold the front wheels while you're strapping them down. I recommend trailers provided you have the storage space for one because they give you flexibility about the vehicle that tows them -- so you don't always have to drive a crew-cab.
You only need a short-term solution. In the long term, your kids will grow, the stuff you take with you will change, and the bikes themselves will change, all faster than you imagine.