Booster seat vs. Convertible

[joanandjoel]

My DD, who is almost 3 and weighs about 30 lbs, is currently in a Britax Marathon. I'm trying to decide if we should move her up to a booster seat (with 5-point harness) and give the Marathon to my 7 month old DS. If so, what is the best booster seat for her age and weight?

Also, what is a good covertible car seat for grandma's car?

[kijip]

Since the MA can go to 60 plus pounds you can keep your 3 year old in it for a lot longer. Since she is not close to outgrowing the seat my inclination would be to leave her there and buy a convertible for the baby.

If $$ is an issue some good combo boosters are the Graco Ultra CarGo and the Evenflo Chase.