You did not say whether they were staying onsite or offsite. Unfortunately, if they are staying offisite you are out of luck- unless they are lucky enough that in the morning they can get to a kiosk and match your times.
We have very good friends that live in Florida and when we spend a week at WDW, they come and spend a weekend with us. They stay at Shades of Green. Unfortunately, for our last trip, we had MagicBands/FP+. Because Shades of Green had neither, there was no way for use to have the same FP+. It really stinks. Now, with everything going FP+ and offsite having access to book at the kiosks in the morning, if they are offsite, there is a chance of them getting there in the morning and being able to get times that overlap your FP+.... but with regular FP being eliminated and everyone stuck with FP+, I think getting FP+ the day of at the times you want is going to be next to impossible soon. Of course, it is expected that WDW is still going to do alot of tweaking and making changes, so no telling what the rules will be in a couple of months, or even next week for that matter.