In the market for 2 new seats, I think

I think I need new car seats..your opinions and advice is requested...

I have a 8 month old, 20lbs, 29 inches moving out of his infant seat and I also have a 3 1/2 year old, 31lbs, 35 inches or so. We are in a Ford Explorer with latchs.

The 3yo is in a Eddie Bauer convertable w/an OHS..we had initially planned to put the baby in the Eddie Bauer and the 3yo in a Century highback booster that was inhareted from family. When I went to install and move the seats into position I noticed the expiration on the Century is 12/06, so it will have to be replaced with in the year. So I started researching and discovered I am really uncomfortable with the baby being in a car seat with an OHS. I would really like two Britax, but can't afford to spend $500+ on car seats right now.

I have seen many positive comments on the Scenera, and I intend to buy one tomorrow for the baby. My big question is, is it safe for the 3yo to continue using the seat with the OHS or should I replace hers as well?

OKay, lets say you do get the Scenera for the baby - how much would you be able to spend on the 2nd seat then?
My basic estimate (based on the fact that my kids hit 20 lbs around 6 months, and one was 40 lbs just before turning 4, the other will be 4 in April and is around 36 lbs) - you'll get at least 3 yrs usage out of the scenera, possibly up to 4 yrs. But we'll go with the 3 yrs. So lets say that in 3 yrs, the baby has outgrown the Scenera. He wouldn't be quite 4 yet, and staying in a 4 pt harness would be the best idea for a while still. Now, the now 3.5 yr old would then be 6.5.
So, I think that getting a Scenera and a Marathon would be your best bet. the 3.5 yr old can use the Marathon now, and is likely to fit in it for at least 2 more years, possibly 3. Then the baby moves to the Marathon and the older one moves to a booster, which he'd then probably be mature enough to deal with.
OR, you could get a Husky (you can find them cheap since they've been discontinued) or a Regent, which would for sure last the older child even longer. Then you could decide whether to switch the older to a booster and put the "baby" (who'd then be 3-4) to the Husky, or get a 2nd Husky/Regent then.
So, in summary - I'd say Scenera and Marathon or Scenera and Husky/Regent.
I'll also point out that your 3 yr old *could* still go RF for a couple more pounds... but I personally wouldn't get a seat JUST for that purpose at this point, since that child will pass that mark SO quickly.
IF you just really can't afford a Britax at all, 2 Scenera's would work and wouldn't cost much at all. You'll just have to get something new when they hit 40 lbs - which my guess is, will be over a year away for your oldest one.
I've heard the Scenera's are on sale for $40 right now at Walmart.

I agree with Kelly's logic, a higher weight limit harnessed seat like a Britax Marathon/Boulevard {I think a Husky/Regent would be overkill since your oldest child isn't large for his age}, Sunshine Kids Radian or Cosco/Safety 1st Apex is a good direction to go for the oldest, because you have a younger child to pass it down to. The Scenera should last your youngest at least another 2 years, maybe 3 years. That means your oldest would get to age 5-6 in whatever higher weight limit seat you choose. Since harnessing is so much safer than moving to a belt positioning booster, I would try to swing a higher weight limit seat.

But, I think this is the way I would do it: get the Scenera now for baby and use the Century harnessed seat for the oldest for now (it doesn't expire for almost another year), as long as you check for recalls and make sure it is in good working order (you also know it has not been in an accident, right?). Ditch the OHS seat completely--break it up with a hammer, remove the cover, cut the harness straps and write on it in permanent marker "dangerous to use" or something similar before putting it in the trash. Then use the coming months to save for a higher weight limit seat.

The Cosco/Safety 1st Apex is the cheapest, at about $130. It harnesses to 65 pounds but has such low top slots that all but the heaviest kids will get too tall before they get close to 65 pounds. Still, it will take almost all kids beyond 40 pounds, which is great. It is sort of a wide seat, but if you only need to fit the two kids in the backseat, it should be just fine. There is a rule that you must have vehicle seatback or headrest at least up to the tips of the child's ears when using this seat, so keep that in mind.

The Britax Marathon/Boulevard have top slots a bit taller than the Apex, but still probably not tall enough to take skinnier kids to the full harnessed weight limit of 65 pounds. These seats have EPS foam (bike helmet foam), the Boulevard has headwings made of EPS foam for added side impact protection. $250-$300.

The Sunshine Kids Radian is new, also harnesses to 65 pounds, but has taller top slots than the Marathon/Boulevard. It has EPS foam and is the narrowest seat of the higher weight limit seats. On sale at least one place for $179, usually $200.