We are 2 adults and 2 kids (42" and 36")
In early October, I asked about RS and FP's when I was on the phone with a CM about something else, and after she checked with her supervisor I was told that both adults (my husband and I) would need a FP to use RS for the first person to go through the FP lane. I then shared that on these boards, because there are many places on the web that say differently. The thread was locked due to misleading info from the CM.
I asked about it again then, because my gut just says that would make sense. A PP mentioned that the real advantage of RS is meant for the standby lines, which I agree with. So my plan is to book FP's for my husband, tall enough child, and myself... but still ask for the RS at the FP lane so both my husband and I have a chance to ride with my tall enough child. This gives her two rides on her 1 FP, one with each parent so she doesn't have to choose, and I don't feel bad about that in the slightest. I am not worried about the too short child missing out on a FP, he's 3 and is going to think just being there is amazing. We will use the 3 we pre-booked up early (and include at least one we can all ride together), and then add the others as we can throughout the day.
I really also don't judge anyone who doesn't book FP's for the whole party of the ride they plan to use RS on. This was my plan up until this thread, but a lot of the thoughts against it made my gut feeling come up again and I don't want to worry about it on vacation.