Clearly the DFP. It's basicly a Momo with a better steering wheel and it turns 900 degrees (and you can set the rotation) while the Momo is only 270 degrees. So I'd suggest the DFP if you have the choice between both.
Naw, I said the DFP is horrible for drifting but the Momo is fine simply because it has less steerin lock. Actually, you could get the DFP and set it to lock at something like 360 degrees for drifting and normal locks when your racing (because you will eventually return to the good side =_=)
Although there are a lot of younger racers who are immature on the track and off the track there are also those who are perfectly fine. I'd suggest maybe throw a quick investigation of the racers past if he is under the age limit?
You mean like half-fixed setups or something? What car would you use? There's no kart in LFS... I'm guessing you'll use MRT? If so then maybe have a setup that feels like a gokart and only allow some changes and then you'd need a parc ferme at the end of every race and qual to check the setups.
Seems interusting, if I wasn't in many leagues already I'd consider it.
G25 is fine if you use the steering wheel locks that LFS gave to the cars (maximum 720)
And Shaun, no FFB isn't fun. At least not for me, its kinda pointless getting a FFB wheel that can go 900 degrees and using 180 of them with no FFB. Basicly it would be easier to get one of those small, cheap wheels that cost 10$...