I put in shoulder belts, and had my kids in the car since they were in booster seats. I've had a car seat in there, but it honestly sucks. Best of luck with three. I'm thinking you'd have to get a bench seat from some other car and modify it to work. Don't forget a third set of seat belts. I don't think it'd be worth your time..they won't stay small enough to be three wide very long.