if you two want to different apps at the same time, get 2 touches. If you want one big screen or want to run apps that only work on the ipad, then get one iPad.
iPad
ipad 2
Is an iPad better to download and play karaoke songs than an iPod
An iPhone. The iPad and the iPod can't make regular phone calls.
Currently, the iPod Touch is better than the iPad, since the iPod Touch does pretty much everything the iPad does, except in a smaller size that fits in your pocket.
Ipad
Well, the only difference between an ipad and a big ipod touch is that an ipad is slim and is bigger
No not that I know. because the white iphone's are no better than black i think they just made white to have a special unique iPod :)
ipod shuffle
ipad is much faster
No. The iPad requires much higher wattage than an iPod or iPhone. While the two smaller devices might fit on the dock, it is not recommended that the dock be used to charge anything other than the iPad and iPad accessories.
There is no iPad 4. There have only been 3 generations of iPad released, but yes. Hotspots can be used with all iPads, iPod touches and Mac computers.