Just stuff him full of food whenever you get into the car! Hehe...

We're facing a similar dilemma. I will be getting DD a booster I think, though like A she's slightly under the weight limit, she's tall enough and age wise she's jsut about old enough too, we will still use a H harness though. And like you, DS is almost big enough for one too...I think we will wait to get him one though (besides the fact that they're soo bloody exxy!!), since he's barely 2 1/2!! Baby will be getting DD old baby seat which is reversable.