You can disable the front. I've disabled mine for over 2 years now by disconnecting the passenger airbag, plugging in the cap on the airbag and putting in a resistor on the end of the harness. Driver airbag still works, passenger airbag doesn't and airbag light stays off like normal. I went this route because I couldn't get any of those aftermarket airbag disconnect companies to return my emails!
As for carseat, don't be cheap. Buy a top of the line Recaro Young Sport car seat that has full giant leg,hip, side, head bolsters belt into it. It'll set you back nearly $300 but it'll fit a child from 20lbs to 85 lbs. Good for YEARS! My daughter loves hers and never fusses about being uncomfortable in it. She does fuss alot when we have to borrow someone else's cheap crappy carseat like the ones you see at target/walmart.
Oh and about carseats, the Recaro Young Sport actually fits very well compared to the others out there. The cheap ones from the department stores won't fit between the hip bolsters of the nsx seat and so they just slide back and forth. Some of them won't even let me close the door. The Recaro Young Sport is a near perfect fit. Not perfect, but near and it's the best it's going to get I think.
Oh and legality. It is legal to have a carseat up front when there is no rear seats in the vehicle. Think: Regular cab pickup trucks, not just sports cars. So for your son @ 7 year old, I'd say yes it's legal no matter what age or weight as long as you follow the law for car seats/booster seats if it's needed.
Sorry, I ended up replying to everyone's post instead of your original answer. Best thing to do, just go after the aftermarket switch.