We tried to do early breakfast at Tusker, then Safari with no FP, and then FOTLK. We didn't make it to FOTLK but that was mostly because Tusker took WAY too long (group of 10, two sets of grandparents and two under 4s). We didn't exit together, we had to wait for some restroom trips, then the 1 year old got super excited about the drummers, so we waited for that, and by the time we got in line it had to be at least 30 minutes post-drop. It was our first morning and my first chance to remind myself it would be different with a big group and to just relax!
I wish I had FP Safari because we did end up waiting in line quite a bit, probably another 15-20 minutes. (and don't forget it's a 20 minute ride too). It's not like there are lots of competing demands on your FP allocation so I could have done it and still gotten the big ones for thrill riders (Everest, Dinosaur).
I think without the breakfast we would have possibly made it - but the other thing I didn't expect was that it was the first time there for some people, so they wanted to take pictures, and then see everything on the entire walk up...which is a long walk....so - is your group REALLY going to be waiting there early, and then walk briskly directly to the ride at rope drop or not? Will they want a nice pic at the base of the tree, then maybe to watch a few of the birds on the walk up, and then slow down to look back at the tree as they cross the bridge...ooh, is that Everest? You get the drift.
Given your group composition - depending on how new people are - I'd probably get it. It's a highlight of the park and one of the few things your entire group will be able to do. And its not like you need to save FP for other things there...