inflatable RIB boat in toy hauler garage?

I had one. They would fit it your TH on a small trailer from Harbor Freight. Weight and deflation was a little bit of a hassle but I would fold it and haul it in my 5th wheel. If you partially deflate it and keep it on the trailer you can travel with it in your TH and use your TV to launch.

Assuming the tail end of the tubes are inflated with nothing solid behind the transom, you could probably buy 12-18" by deflating. Just be careful of chaffing. If the tubes rub against the walls, they will eventually fail.

If you have one of the beds that raises and lowers, you could probably modify it hold the dingy and you raise it up to the roof to keep it largely out of the way.

The bigger issue is how will you launch and retrive it? RIB's are typically a lot heavier than a standard inflatable. Nothing crazy but 200-300lbs for a simple one (vs 60-100lbs for a standard inflatable) and it's bulky and akward. If the wife isn't strong and the kids are young, getting launched and stored will likely be the main issue. There are wheel kits that help but it may be more hassle than it's worth.

when I bought my inflatable quicksilver, I considered a RIB. IIRC there was some issue in semi-deflating it for transport, so be sure to check out how much dis-assembly is required for this.
bumpy

Depending on brand West Marine, Mercury, Zodiac, go to website and look at deminsions. A RIB will definately ride better, but they do make inflatable keels also that can roll up and stow easier. I think a 10' boat would fit best and be great for two people maybe four for very short runs and I mean short runs on flat water.