re:booster seats
Hi! I would start by looking at the compatibility database,
(Carseat Data website closed - link broken). Look up your model year Explorer and see what other parents have found that worked.
For the older boy, I'd look at the Evenflo Express, Britax Star-Riser/Comfy, Graco CarGo, or the Safety Baby Polo/Uno (if you have headrests). I've got pictures on my web site of these seats
www.carseatsite.com/recommendedseats.html. Evenflo has just released a new seat, the Apollo, that looks promising. It has EPS foam which is a nice safety feature. Some places to try for that seat are Wal-Mart and Babies R Us. It was just release about 2 weeks ago, so it may be hard to find right now. Try to look for a booster that will be comfortable for your child and works with your vehicle (i.e. won't tip when you turn a corner).
For your younger son, I'd look for a seat with a harness that will go to a higher weight than 40 lbs. Unfortunately, your choices are very limited at this time. Britax has the Super Elite, which has a harness that goes to 80 lbs. Heck, this would be a good seat for your older son as well. It's hard to find, since it was released in the northeast, though the Toy House
www.toyhouseonline.com has them, I think. If you have headrests or your son's ears are still below the top of the back seat, you could also look at the Britax Laptop. It's an L-shaped fabric-covered foam piece that sits on the child's lap against the chest. RightStart
www.rightstart.com used to have the Fisher Price Futura. The Futura has a harness that goes to 60 lbs. It's worth checking, but they may be sold out. The Futura is no longer made. I feel that your younger son is still too young to sit in just a booster with the vehicle seat belt. Most kids don't have the maturity to sit properly in a booster w/vehicle seat belt until around age 4.
Heather