Tent Thoughts

I'm posting this here in the General RVing forum rather than the tenting forum because I'd like some input from other RVrs on using a tent for additional sleeping space. For several years we owned a triple bunk bed travel trailer but once our boys reached adulthood they were both too busy, not interested much in camping with us any longer so a couple of years ago we moved on to a shorter, lighter couple's trailer which suits the needs of my wife and I along with our 80 lb dog just fine ... we're quite happy with it. :B Recently though our 19 yr old has expressed a renewed interest in camping with his parental units so on the couple of times we've done this he's used the sofa for sleeping and although he seemed to be comfortable enough privacy was non existent and his personal belongings really cluttered up the camper! Since he's in university about the only time we see this happening is during the warm summer months so we're now thinking perhaps a tent may be the solution, though because use would be infrequent I'd want to limit the cost to perhaps $150. Obviously there are an endless variety of lightweight one and two person tents that would do the trick but they all require some sort of annoying setup ... recently though I became aware of the Coleman Instant Tent 4 which is currently on sale locally at Canadian Tire for ~ $142 + tax. The main attraction is that set up and tear down each take about a minute as the poles are all pre-installed ... the downside is it doesn't come standard with a fly and although one can be purchased after the fact any reports I've read said it's not fully effective anyway. I think I could solve that easily with a tarp and although this tent is certainly much heavier & larger than a back pack tent I can easily store it out of sight, out of mind in the trailer yet have it available anytime we may have an occasional need for additional sleeping space. As one who hasn't tent camped in decades my question therefore is - does this tent seems like the solution I'm looking for or should I be sticking to a more traditional style of tent from brands such as Eureka!, Marmot, Mountain Hardware, etc, that are sold by camping specialty stores? :h