Booster Seat advice

Hi there! I'm looking for some advice and hoping the community can help me resolve my situation! I have twin 5.5 year olds, both 38 lbs and 42" tall and a 19 month old. My smaller car is a 2009 Subaru Outback Wagon and the only way I can fit all three is with a RF Combi Cocorro and two FF Sunshine Kids Radians.... but it's tight, let me tell you! My other car is a 2013 Pilot and I have a RF Radian 100 for the baby and the twins are still in Britax Marathons, which were manufactured 8/08. I'm trying to figure out how to replace the marathons with boosters for my twins for the Pilot, and then also figure out what the best solution is for them for when they go on field trips and I have to have them carry their own seat for a parent to install should I not be able to chaperone the field trip. I fear that the low back boosters will not work well given they are so short and I'm unclear if other parents will take the time to put a clip on for Field Trips. But I'm not sure if the high back ones will be too heavy to lug around, and am also concerned that they might be too big to fit into the subaru. For longer trips and weekends we always take the pilot, so my preference is to move the radians into that car so the twins will be in a 5 pt harness vs. the sholulder belt/lap belt of a booster, but that would necessitate me having very narrow booster seats for the subaru. Of course, I can also sell the radians since they still have a good 5 years of life left in them and replace all seats with the boosters, if the 5 pt of the radians isn't truly "that much more safe". Budget is not an issue, but clearly, I'd rather not buy a zillion extra car seats just for special occasions, etc. I so appreciate any response. I realize I'm rambling a bit! thank you!!

At only 38 lbs I'd keep them in harnessed seats. It will also be much easier to buckle them in harnessed seats in a super tight 3 across then in boosters. I'd look at getting them Harmony Defenders to replace the Britax seats.

I think that you're going to have a really hard time fitting two boosters in your Subaru and still having room for the children to buckle the seatbelts. The only option that I think would really work is to get two Bubble Bums, or possibly Harmony Literiders, both of which are backless boosters, and you wanted (rightly, I think) to avoid those for the time being. You might think about Ride Safer Travel Vests, as those would probably work in the Subaru, although wouldn't really work for carpooling if you're not with them (I don't think). However, maybe using RSTV's for the subaru and getting boosters for other people's cars, field trips, etc would work well.

If you're not needing to think about fitting two boosters in a 3 across in your Subaru, I'd probably go with Graco Turboboosters as a light and easy to use choice. They are an IIHS best bet choice, meaning they fit a wide variety of kids and vehicles.

I think a lot of people really do underestimate the kids with RSTVs. Both my 7yo and 6yo (5yo at the time) can buckle and unbuckle the RSTV by themselves, properly, but neither one could do the bubble bum, even with practice.

So the twins are not riding in the expired Marathons, correct? I just want to make sure.

the twins are in the marathons, but the DOM is 8/09 (not 8/08 as I indicated, so I've got a bit more time with them.
That said, it sounds like I have to keep my radians in the subaru for space reasons, which would mean buying a couple of backless portables for field trips and then more "permanent" high back boosters for the pilot. So, that being the case, should I really keep the twins in a 5 pt harness or can I feel safe putting them into a true high backed booster in that car?

thanks!