You're still in PA, right? How much were you looking to spend? What are your priorities for space needs/uses? Were you looking to get unplugged from the inlaws house?
I'd be tempted to continue using the RV for some things (bathroom? kitchen?) but maybe tear out/reconfigure some bits to make more space or more to your liking. Use it for kids rooms and get a 16-20' yurt traditional-style yurt (felt
, easy setup/takedown, simple platform possibilities) to use as your bedroom/additional space. It would keep costs down ($5-10k?), be easier to heat than something bigger, and give you some more room.