I have people over all the time playing Wii, I've only used more than two nunchucks for Redsteel...

Get Wii Play, it's fun with non-gamers and girls.

GC controllers are better for brawl, Classic are better for VC games IMO.

If you don't own GC controllers, then the Classic are a pretty good idea.

I didn't buy it all at once, I bought as I needed.

If you just enjoy playing the game, then I would suggest you get a total of

3 extra Wii Remotes
3 extra Nunchucks
1 classic for the Virtual Console if you plan on buying many games.

as this will allow all of you + 1 friend to play SSBB or any other game, plus for games like Mario 64, you don't have to contort your hand by using the Wii Remote + Nunchuck combo.

If you are a "hardcore" must win at all costs type of person, or your so stuck in your ways that you can't adapt to a new controller, then

3 extra Wii Remotes
1 extra Nunchucks
4 extra Wavebirds/GC controllers.

also, I suggest this for rechargeable batteries

http://www.batteryjunction.com/ch10chsmchwi1.html

but the c-stick is completly redundant and useless, because you can't charge up your smash using the c-stick. However, I do like using the classic controller I have becuase I can hit special, attack, and jump a lot faster, but the Wii Remote + Nunchuck work fine.

Assuming you don't want to spend more than you should.
Among you and your 2 sibling, you should get 1 extra set of wiimote+nunchuk.
Most games feature 2 players co-op, so, it's neccessary.

Get a wavebird as the third controller option or use your existing GC controllers.
At least 1 of you would be comfortable with use it for smash.

If you're worried about having enough controllers for parties, just ask the guests to bring their own mote/chuk.

Classics controller is optional depending whether you are interested in VC.

I didn't understard if you will be 3 or 4 players. However here are my advices:

1. get a Wiimote for everyone

2. buy only 1 extra nunchunk

3. buy 1 warebird

4. buy 1 classic controller

After playing for 1-2 weeks with all this controllers you can then decide if you need any extra nunchunk's, wavebirds or classic controllers.

Some of you will like the wavebird for SSBB for example, while others may like the classic controller more. So that's why is best to get only 1 of each and then decide what you need more.

you got GC-controllers?

if so, then just get 3 additional wiimotes first. WiiSport tennis with 4 is just a lot of fun.

My recommendation is:

Wii Play

2 Extra Nunchuks

Extra Wii Remote

Gamecube controller OR Wii Remote + Classic Controller if you want a fourth player

This way you and your siblings will each have a Remote+Nunchuk plus an extra remote when someone comes over. I don't think you will ever need 4 remotes + 4 nunchuks (there aren't many games that use that) so you're better off with a Gamecube controller or a Remote + Classic controller for the fourth person.

For the fourth player the Remote + Classic will be much better (for Wii Sports) but the Gamecube will be a lot cheaper (you can get a 3rd party controller for $10). Since I'm assuming money isn't a huge factor (might as well splurge all the way) I'd recommend the Remote + Classic. The Classic is only for 4 player Brawl and Virtual Console games.

Wii Play has a couple fun multiplayer games and it's only $10 plus remote.

I'm sorry if that's confusing, but let me know if I helped.

Good luck!

Well, all you need is the Wii mote + nunchuk you have for Zelda and Metroid. I'd buy a second Wii mote + Nunchuk for Wii Sports if you wanna box each other, and another Wii -mote for Tennis.

So that's 2 extra wii motes and 1 extra nunchuk.

No need for classic controllers, if you have a gamecube controller.

Follow DMeisterJ advice. And if you really want to tennis with 4 ppl at once then get the fourth wiimote. There is no need for more then two nunchucks atm.

Skiip the zapper, get the Nyko Perfect Shot. MUCH better