RE: Is the Regent the right seat for DD? Also, $221 shipped a good deal?
I actually think that she is going to be more comfortable staying in her MA as opposed to moving to the Regent at age 2. I would be inclined the get the baby his own MA when the time comes. I know my 3 year old still falls asleep in the car a lot and the Regent is not going to be as comfortable as that. She can get up to 2-4 more years out of the MA, it would expire before your son outgrew it anyways (assuming it is 18 months- 2 years old now).
For the second seat for her (assuming that the RA goes to DS), I would look at the Apex if your truck has high headrests or at a Graco ultra Cargo type seat.
Katie, mama to a pair of boys.