Harness or HBB for small 5.5 year old?

My son is 5.5, 32 lbs and 39". His Britax Marathon expires next year and I am trying to decide what to do. I have always thought that harnessed was safer (we are in BC, Canada, and I had understood that because he was not 40 lbs he had to be harnessed), so I am trying to decide between something like the Frontier XT or going to a HBB. My daughter is 3.5 years old and 31 lbs, and close to the same height, so I am wondering if I should pass her Britax Boulevard on to my sister, and move her into a Frontier as well... I would love suggestions. Thanks!

I'm not a car seat tech or anything, but from my understanding it's always better for kids to be in a 5 point harness as long as possible.

A high back booster provide at least as good safety as a 5-point harness for older forward facing children (4 and up). There is no research, data, statistics or real life experience which show 5-point harness is safer.

The idea that 5-point harness provide superior safety is a common myth in US and Canada. A 5-point harness does just like a high back booster provide good protection although nowhere near as great as rear facing seats.

When using a high back booster a good belt fit across the chest is important. That's usually fine with a child your size.

While at your son's age, it's true that a HBB should be as safe as a 5 pt (though, unlike adventuredad, I prefer not to see that switch until closer to 6 since most 4 y/o are too impulsive to sit properly in a booster). That said, legally in Canada, he cannot move into a booster until 40 lbs.

Hello and welcome! As has already been confirmed, your children will need to be harnessed until they are 40lbs. For a slower gainer, another 2-3lbs might mean a year or more (based on my own experience!). Your son is very small, and while he is physiologically more mature as well as mentally more mature and developing good impulse control, and on those counts would probably be quite safe in a booster, he still does not meet the legal minimum weight and would likely fit more "loosely" in the booster seat, putting him at risk of submarining (slipping under the belt). I would definitely get another harnessed seat like for him. When does his current seat expire? (month) When does your DD's BV expire?

You can choose to get a combination seat that turns into a booster, or you could find a great sale on a convertible seat with tall slots and then follow it up with a dedicated booster later on. Price-wise this often comes up about the same in the end, and it gives you the option of continuing to use the harnessed seat full-time while also booster training and using the booster for carpools, rides with family members, etc.

How much room do your kids have left to grow in the harnessed seats they ride in now? Are they on the top slots, and how many inches do they have left before they reach those top slots? The straps have to be at or above the shoulder for FF, so if they are both quite close to the top slots I would look at new seats. Ones with the highest possible harness slots - which is the FrontierXT as you have determined. :thumbsup:

However, if they have lots of room to grow, I would personally replace just the expiring seat and leave your DD as is (that is, unless you want to be really nice to your sister and are looking for an excuse to get two new seats ). I would get a new seat for DS that has taller slots (either a convertible or combo whichever has the best price), and then get a booster like the highback TurboBooster or Britax Parkway or whatever great new booster is available when DS finally reaches 40lbs, and pass down the harnessed seat to DD at that time.