Ideas for 3 cats?

If you're like us, a new home is not an option. We don't full time but are retired and take long trips. We started with four cats but we are down to three now. I think you will find that it will be much easier than you think. The cats will find their own areas of comfort during travel. One of ours finds it in DW's lap. While parked we have a folding "playpen" so they can have some outside time. The squirrels in Yosemite would actually walk up to their playpen and shake their tails at them. Drove the cats crazy, but they enjoyed it. We have a 32" C so the litter box gets moved to the cab between the seats at night and in the bedroom next to the bed during the day. We got one of the plastic storage bins at Walmart and cut a "U" shaped entry into it for a litter box. The only problem that we have is the cats like to go from window to window at night watching whatever animals happen to be in the area. But they're enjoying themselves so it is all right.
Go for it. I think you will enjoy having your cats with you. We surely do.