We will be having a #2 in April, so this is a little far off still, but we like to plan ahead. Our DS will be a smallish, 4 year old when the baby arrives and we can't decide what to do for carseats. DH wants to get oldest a convertible that turns into a booster and have the baby in DS's Britax roundabout. I am not sure about either option, we are wanting to save money, but safety comes first. Is is best to let DS stay in the Britax as long as possible or are those convertible 5 harnessed booster seats really as safe? Also, DS had an infant seat, which we no longer have, so I have never had an infant in a convertible, especially the Britax, which I really found to sit very upright rear facing. Suggestions greatly appreciated.
The roundabout will not fit a newborn. So you will need another seat for the baby at least for a few months. And a newborn must be at a 45 degree recline. It's fine to be more upright when older.
The forward facing 5 point harness seats are just as safe as convertible seats. They all pass the same testing standards.
How much growing room does your ds have in the roundabout (it's outgrown when his shoulders go over teh top slot OR the weight limit is reached OR tips of ears are above the top of the shell? When does it expire?
For the baby, if you want an affordable infant seat that will last a long time I'd look at the safetyfirst onboard35. If you want a convertible that will fit a newborn take a look at the graco myride or first years true fit work well and have nice padding. The radian is a good one too if it will fit in your car.
If your ds needs a new seat, look at the evenflo maestro, graco nautilus, or britax frontier.
So, I just double checked our actual carseat and not a website, and we actually have the britax marathon, does that make a difference? My DS is about 38" and 32 lbs. So I am not sure how big he will be in 8 months, but probably not much bigger I would imagine, I would guess he is not going to outgrow the seat that soon, but DH wants to save money. We are just trying to not buy so many carseats, 2 new seats eventually vs. 3...
The Marathon will not fit a newborn either.
For your cheapest option, if you think your ds will make it to booster age/size in the MA, keep it for him. Purchase a convertible that fits newborns for your baby. Your ds will need a booster eventually (the turbobooster is around $50, so you can get one inexpensively), but the baby should be set for 4+ years.
Or, get an infant seat for the baby. When the infant seat is close to being outgrown, pass the MA on to the baby and get your ds either a harnessed combo seat or a booster depending on his size, age, and maturity at that point. I don't know when your MA expires, but hopefully long enough that you can either pass down the combo seat or re-evaluate at that point.
Secondly, the manual will explain how to size the seat. One of the requirements is that the infant's shoulders must be AT or ABOVE the bottom most slots of the car seat. Because the bottom most slots are 10" from the seat pan, children have to generally be 26" tall (roughly) before their torsos are tall enough to reach the bottom set of strap slots.
Most kids are around six months old before they fit safely or legally in your convertible.
Your marathon has a label on the side of the shell, near the top of the seat. That will tell you its date of manufacture so we can figure out when it expires.
Have you thought about what kind of seat you would prefer for your new little one?