Comparing DQ to IOA/Universal is comparings apples to Watermelons. One is a 1/2 day of neat games, and the other is two full sized theme parks. It will also cost you twice as much as IOA/Universal as well (and maybe more, since some tickets include DQ). My parents (68) liked DQ for an hour or two, but they spent three days at IOA/Universal. Your teen could probably spend a few hours at DQ, and your 6 year old will enjoy it too. In fact, you could probably drop your teen off there for the evening (or maybe an afternoon when you could do Fantasy Land type rides he might not appreciate). He might enjoy being trusted being left alone for a few hours. We dropped our two 14/16 year olds one year, had a really nice dinner as a couple, did some shopping, and met them at a specific time. We all enjoyed ourselves more because of it. They even made friends with some other kids who were younger. Note, cell phones did not work in the DQ building, so beware.
Teenagers generally like IOA/Universal better than the WDW theme parks (generally, I said, YMMV). It is generally more adult and more realistic and for this reason may be too scary for your younger child. The Earthquake ride is much scarier than the backlot tour, for example. Men In Black blows the pants off Buzz Lightyear (of course, MIB was built from scratch, and BL is a recycled ride from Eastern Airlines).
There are certainly things your younger child will like at both these parks, but how much depends on his/her fear level. Some six year olds I know love Universal better than WDW, but I would think that the majority would love WDW better. Universal is kind of like MGM Studios, only bigger and more realistic. IOA is a themed amusment park. Spiderman is about the best ride anywhere, but most of the rest are thrill rides and may have significant height restrictions. There are rides for younger kids (Cat in the Hat, One Fish Two Fish) and some shows they might enjoy, but it is geared for teens.
Couple of things. Looks like you will be there around Thanksgiving. One thing to consider is that at Universal/IOA, if you stay at one of their three onsite hotels, your room key gives you front of the line access to most rides. One day at their hotel is two days of front of the line access (one day at each park). Or, you can buy a book of front of the line passes (one per ride). Note, they can sell out of these on any given day).