If your wife and kids love the Wii, i don't see any reason to sell it.

As for MKWii, definately a must-have title. And in comparision to MK64, 64 had better tracks (i think 64 has the best tracks of all Mario Karts) and MK64 had 2 player GP (as racing for the trophies), which MKWii doesn't have. Although, MKWii has the possibility to customize the rules for multiplayer (even in battle as someone said it's broken, which it's not when you adjust the rules to match the previous Mario Karts).
MKWii also has awesome online, with ghosts you can download, send to you friends, online battle, online GP, time trial records list for WW, continental and friends, competitions.
Boost have been renewed, so that karts have 2-phase boost after sliding, weak and strong and you can get boost from jumps too. And a completely new feature is to be able to drive with bikes. And driving with Wii Wheel is great.

If you are going to sell your Wii anyway, get Mario Kart Wii first, it's definately a game you do not want to miss.

I dont mean to sound argumentative... but i think its awfully silly to trade ANY console in after only playing 4 games...

With a trade in you are going to get at MOST half what you paid for, which obviously isnt very consumer friendly.

 There are many great games to play on the Wii, for you and especially for your family. And if you are a gamer(which you obviously are if you are on this board) im willing to bet a couple of months to years after trading it in you're gonna want to buy the Wii back(the library of games is only going to get bigger and better). I've seen it happen to quite a few of my friends already. 

yes

You should keep your Wii and buy MK and Boom Blox with those two games your family will love you for ever!

I really hope you are not actually thinking about putting ANY eggs in the Banjo Basket.... I really feel that it will fall short.

My Mario Kart Play Count is on about 50 hours, but Most of that has been multiplayer so its somewhere in the region of 100 man-hours

It is alot better than the 64 or gamecube versions - 12 players per race, using the Wii wheel, online play, single player actually takes some time to complete, lots of tracks.

Buy it - I'm a nerd and now i have a social life thanks to it :P

What games interest you in Xbox360?

This game is fantastic. I love it. Also, as much as I used to love Banjo-Kazooie, Rare is not really the same team as they once were and I don't expect much from it. Even when it was a great game, it wasn't as good as the Mario platformers in my opinion. Also, If you liked Red Steel the sequel is supposed to be much better.

Mario Kart Wii is fantastic! I play Mario kart series since SNES. I own MK 64 on VC and the Wii version is faaar way better than the 64 version.
For more fun, you should have the online.

I don't like MKwii, but the Wii is worth it.