There only is one type of iPod Touch, the differences are all about how many songs it will hold.
So yes they all have wifi, etc and are easy to set up.
The biggest question then is how much music he'll want on there.
If you can, get a sneaky look at his iTunes library (just open it up). Click on the "music" option under library (top left if iTunes menu).
Once that's up, have a look at the very bottom and you'll see it gives you a summary of the entire library in terms of how many songs, hours, days etc of songs he has. In there should also be the number of gbs of songs he has.
The most expensive model is the 64gb, which is pretty big and would suit most. However if the Mr is a bit of a music nerd and has a supersize library bigger than this, he won't be able to fit the whole library on there.
As iPods are now more than just MP3 players, it's all about who you're buying it for.
If he's after more than just music and the whole portable video, internet, email, applications and games techie stuff, then the iTouch is great fun. The compromise is that you have to be selective about the music you load on because you can't fit as much on.
If he really isn't that fussed about loads of music choices, happy to create his own playlists and is more interested in the other side of the iTouch, then don't worry about gig size (especially as price increase considerably with increase in gb size).
If he is a music nerd and likes carrying around his whole collection and isn't that fussed about the internet and toys, the maybe the iPod classic is more for him.