I have a 98 CRV that I've done lots of combinations in. The Civic should be the same in terms of back seat room. Here are a few that work:
Radian Radian Literider
also works with a TurboBooster, and I know the high back version would fit there as well:
RF True Fit, FF Radian, Nautilus.
This is a different car, but I've done it in my vehicle too and it works:
Keyfit, Nautilus, RF Radian
RF Marathon & Radian, High back Turbo Booster
So, the short answer is you're going to need at least one Radian in each car. Easiest would be to put it FF in the center for the 2 year old and then you have lots of options for what goes on the other side. If you're not opposed to a convertible seat from birth, the True Fit combo I have up there would be a great option - you could put the baby RF in the True Fit from birth, put the 2 y/o FF center in the Radian, and put the Turbo Booster next. If you want to do a bucket seat, a Keyfit or Snugride will work outboard next to a FF Radian.
For even more room, buy two Radians, put the baby RF outboard, 2 y/o FF center, and then you have tons of room for whatever booster you want, and by the time the 2 y/o gets to booster maturity, you'll be able to FF the youngest in the center and have the other two booster riders on the other side.
A PP said she got a Radian RF in the center - both myself and a CPSTI have tried and tried in my vehicle and have been unable to get a successful install.