Another plus to the Nautilus is that you can use the
LATCH sytem when it is transitioned to a
booster. This will allow the booster to stay in the vehicle instead of riding with your child in a crash.
One thing, keep an eye on your dates on your carseats. All the ones listed (except the
Radian) have 6 year life spans from the date of manufacture. So, be sure to keep an eye on that
The
Regent, by far, will be the best bet for your
ds--as far as being in a harness. Make sure you read the manual as it has a few 'tricky' installs and certain things that you can and cannot do pertaining to his weight. IF he outgrows it before it expires and it fits your dd, you can easily purchase a new cover (if you want to girl it up--the Madison) to fit HER taste (LOL--I have a GIRLY girl).
Sounds like you have everything ready to go!!!