I have a tiny 24-pound DD rear-facing in a britax advocate in the second row captains chair, a new baby coming in November who will be in a Chico keyfit probably, in the other captains chair second row, and my older two (DS is almost 5, 45', 50 pounds in a britax frontier 85 SICT, and DD who is 47' and about 48 pounds, but will be 7 in July, also in a frontier 85). I planned to harness them both to 85 pounds, but with this stupid one anchor thing, I can't have them both in the back, which makes the most sense convenience wise. Is it ok to transition the 7-year old to a parkway or other high back poster, and keep the 5-year old in the frontier when baby comes in November? She will be 7 years, 4 months and is pretty mature doesn't really fall asleep in the car, etc. for some reason I am feeling guilty about this!