Yes, there are still some Nintendo faithful out there. I consider myself one. Although I'm no longer Nintendo exclusive, I still grab Nintendo products first. You just have to realize that you are in the minority or the Wii U would be doing better. Most experts have the PS4/Xbox One moving 2.5-3 M boxes this holiday. That's basically going to wipe out the Wii U lead and put the systems neck and neck after just a couple of months.
There is some truth that the market is ready to move on from Wii/PS3/Xbox360. As such, most consumers will wait until all options are released before they jump into a new console. But the Wii U is no longer an unknown. It's known that most big games will not only be optimized for PS4/Xbox One but will skip Wii U entirely. It's known that the Wii U is not a hot commodity while the other two will be at least this holiday season. Consumers love hot products it's in their DNA. I just don't see the bump being very significant for the Wii U. It has games now, has better bundles, and is still selling poorly. It needed to move 300,000-400,000 a month during the game slow first year. Not, 460,000 over like 9 months. That's abysmal and difficult to recover from.
While I've argued that $ is important in the handheld arena (you have 3 3DS and most families have multiples) I don't think it's that important in the console arena. I know families with multiple Ipads for their kids and they think it is the best thing ever. Most 11 year olds have smart phones of their own. Ipad can charge more than Androiod tablets because it's perceived that it's a better product with better apps. Sony/Microsoft will have this advantage over their Nintendo this round.
I know you seem to be a reasonable parent with reasonable limits for your children. But don't expect most parents to be this way. Tommy's going to come home and say "Mommy I played the PS4, it is the greatest thing ever!!!! I love it, I want one, Please, Please, Please, Please, Please!" And most parents will buckle. Especially because $300 is still alot of money. If you have trouble justifying the extra $100 between something your kid wants and something your kid doesn't want, you might as well save your money and say no to both options.