Wow, so many replies already ... thanks to all! :B
I've just returned from one of our local camping specialty stores (SAIL) where I gathered some really good information that I can now relate to how we'd use this tent. First, here in the Ontario provincial park system and local conservation areas which is where we'd be using this tent there are no restrictions on setting up a tent along with our travel trailer ... IIRC in the prov park system it's defined as "up to 3 shelters" that can be any combination of trailer, tent, dining shelter, etc as long as only one of them is a trailer. Secondly, thanks so much to Impkitti who reminded me we already have a perfect location for a tent as long as it's not too large - under the awning where I already would have an under awning ground mat laid down. Even though we have a Dometic 9000 power awning it does tilt down significantly at either or both ends and I've found it not to be an issue leaving it deployed even in heavy rain, only putting it away if the wind really comes up, so having the tent under the awning would really keep the setup simple. We normally maintain a pretty clean campsite and at night I usually put all our chairs, etc, away in the trailer's pass through storage compartment, if for no other reason than they won't get wet overnight from dew, so the area under the awning is usually vacant and could easily be used for spotting a tent ... during the day these tents are so light weight we can just pick it up and shift it off to the side, out of the way. As for the suggestion regarding height IMO this is a non-issue as we'd only be using it for sleeping ... most backpacking tents don't offer much interior height either and those owning them seem to get along fine with it. We had discussed using the back of the Avalanche and while my son wouldn't have an issue with that it would mean unloading all the "stuff" that I normally just leave in the back of the truck while we're camping, only removing it as we may need it. Comments regarding the Coleman Instant Tent 4 are well taken and now that I've seen the alternatives I think I'll pass on it and focus on a smaller, lighter weight backpack style of tent. While there certainly are some really nice Big Agnes, Marmot, etc, style of tents I really think they're overkill for the purpose I have in mind but the store did have a lesser known but decent quality Yanes model on sale, available in both a 2 or 3 person version. A 2-person model in any of these types of tents would be plenty for 1 person but the somewhat larger 3-person model which would easily accommodate 2 people could be just that much more useful those times we might have friends wanting to join us, as just was the case this past weekend when one of my wife's BFFs and her daughter camped on our site. They had their own borrowed tent but it was ungainly and difficult to put up so having our own system stored in the trailer, along with a couple of sleeping pads, would allow us to enjoy the company of friends or relatives with minimal effort. I did just buy a twin size air mattress for our son but because of the width two of them would only fit a 3-person size tent, however if I instead invest in a couple of self inflating pads they'd both easily fit in the Yanes 2-person tent that is on sale for just $120. The next step is to drop by the store with my wife so she can see what I'm considering here but in the meantime any further suggestions / comments are quite welcome. Thanks again to all who have replied! :B