If you are truly there at rope drop (i.e., before they start walking people back to the rides), it honestly won't matter which of those two rides you get a FP for, as it should be purely a bonus. You can just choose whichever one they like better. And as
@DavidNYC suggested, it probably makes sense to move that FP up to 9:15 or so, which will allow you to use it any time before 10:30 based on when waits actually build up, and then you can set up your other two FPs for earlier as well which will allow you to either ride Star Tours earlier or burn whichever other Tier 2 you book so you can try to grab additional Tier 1 FPs earlier in the day.
We did rope drop at HS twice last week and headed up Sunset Blvd both times. We rode RnR first and then Tower twice by 9:20 each day. We could have very easily done RnR twice before moving on to Tower, but my daughter likes Tower better so that was the higher priority to do 2x. In any event, doing RnR first makes some sense because the overall experience is so much shorter (especially given that you skip the pre-show at rope drop). So if you want to do both, then doing RnR first gets you moving on to the second ride quicker, and in theory before any meaningful waits start to build.
For the sake of using round numbers, last week let's say there were 5000 people in the park at rope drop. When they started walking everyone back, roughly 4900 of those people were either going to Slinky or the Falcon. If anything, once Rise opens, rope-dropping Sunset Blvd will only get more pleasant, even if the overall park is more crowded. They should have absolutely no trouble riding both rides, likely more than once, before they'd even need to think about scanning in for the first FP.