Now that's some advance planning!

Love it.
I often book flights without adding my CP at that moment, so that I can easily change my plans around (harder to do when there's a CP attached to your ticket). The risk, of course, is that a seat will disappear while you're waiting. That has happened to me before, where the seats were sold out on a particular flight. But I obsessively checked the SW website, fully prepared to cancel my plans (since I couldn't leave DD home by herself) and when I saw a spot open, I snagged it.
Part of the decision, I think depends on how many flights are available on that route on that given day. If there are 20, that's different than if there are only 4, since with a limited supply the chance is greater that seats will be sold out.
Since 2024 is a ways away, you could look at getting as many URs as possible in the meantime so that you have enough URs to transfer to SW and book for everyone. Then after you've gotten your CP, cancel the children's flights and get those RRs back. Yes, you'd be left with RRs instead of URs, but I personally see RRs and Hyatt points as the best value for URs anyway. Especially if you have a CP.