A motor home is one extra motor vehicle to insure ($) and maintain ($$). Your Expedition should be able to handle a trailer of reasonable size. I'd suggest limiting that to something under 20 feet overall length if possible, and under 4,000 lbs dry (unloaded) weight.
Unfortunately everything is priced at a premium right now. You'd be better off waiting a year or so until demand falls off somewhat. In the meantime you could still have a great time with a $150 tent, some sleeping bags, and a simple propane or butane stove (one or two burners). That's how I took my two kids camping; I couldn't afford a trailer until about the time they were graduating from high school. But if you really can't resist the bite of the trailer 'bug', a popup will be your best choice because it will cost less to buy and also cost less to tow (the low profile means better gas mileage... wind resistance costs more than weight when towing at highway speed). Besides, a short and easy-towing popup expands to a much greater length when set up.