Welcome, and congrats on the newbie!
Now. That generation CR-V is so not car-seat friendly. That tiny middle seat is a bugger. We recently traded in an '04 CR-V, and it and I had many disagreements over car seats.
I'll start by saying that I don't have any experience with boosters in the CR-V, but I have done two RF convertibles side by side on the 60% side of the split and also a RF seat + FF seat, again on the 60% side.
Since your oldest will need room to buckle his booster, I'd start out planning to put him on the 40% side (behind the driver) and then try to figure out which seats will work for the two younger ones on the 60% side. I don't have any experience with the Harmony V6, but the stand-alone/40% side of the split is pretty roomy, so I imagine most boosters would work well there, as long as the
booster fit is good for your DS.
As for your current seats... yikes. Both the Nauti and especially the Frontier85 are pretty wide. I really don't see either of those working in a 3 across, especially with an infant seat. The only way I can *maybe* see it working out is if you put the baby in a convertible that can puzzle with the Natui's armrests. Maybe.
Are you willing to consider a convertible seat for the baby? DD went straight into a Combi Cocorro, and I actually preferred that over the infant seat that my DS used. Also, that's a nice, narrow seat, and it lasts longer than many infant seats. DD still fits the CCO RF, and she is turning 2 next week.
Have you tried any installs on the center seat yet? Most harnessed seats are tricky to install there. However, a RF MyRide65 goes in like a dream. Also, the MyRide sits up high on a base, so although it's a wide seat, low profile convertibles can often puzzle under it pretty nicely. Maybe a MR for the newbie, and a low profile FF seat next to it for your 4 yo? I know that I managed a RF MR in the center next to a RF Radian. I'm not sure how a RF MR/FF RN would work, but I don't think they would fit quite as well. The MR tends to puzzle best with seats that are facing the same direction, IIRC.
My personal set up was a Radian XTSL next to a Cocorro on the 60% side of the bench. There was then enough room for an adult the sit behind the driver, so I really think a booster would also work. Granted, the RN (or a newer Ranier) is pricey, but if your budget allows for it, but it could be passed down to the baby later.
Here are some pics of my side-by-Side RN + CCO set up. Both seats were solidly in there, but it was a tricky feat to pull off-- and those are two very narrow seats. I realize that your 4 yo is FF. I don't have any photos, but I did eventually turn the RN FF, so DS was FF in the center in the RN, and DD was still beside him RF in the CCO. I found getting the RN to FF in the center to be especially tricky, but it was doable.
A tip to help with installing on that center seat: You can twist both buckle stalks (the regular one + that one for the shoulder belt that comes from the ceiling) up to 3 full turns
each in order to shorten them, if necessary. Most of my installs did require both stalks to be twisted.
The
Successful 3-Across thread might give you some more ideas. Good luck!!!
