We need to fit 3 car seats at the back of a medium/large sedan/wagon.

One is a toddler who will use a Radian very narrow heavy like a tank car seat.

But 2 kids aged around 5-7 would need more secure seating than a booster bum seat, but more comfortable than a rock hard phil and ted full body booster cradle that is no good for long distance.

Any one knows where to get some safe, easy to buckle, narrow (ie not very wide), comfortable (padded) for long distance driving car "booster" seats?

Thanks