The only way to do this now is to save each waypoint as a favorite and navigate to each in turn. Even with everyone using Waze, for privacy, everyone's position will not be accurate in the app. The only current way to see almost exactly where someone is, is using the Send->Drive feature, which sends a weblink from which others can watch your location in near real-time, but it's in a browser, not in the app.

I wish that Waze had this ability since I frequently plan out scenic rides for a car club. I've found that Co-Pilot is a good GPS app for this and you can make driving routes directly from the app pretty easily.

Currently, you can only have one waypoint on a route and you cannot pre-plan the route. For multiple cars, Waze does work nicely for being able to know when each will reach the shared destination. However, you are still limited to only one waypoint. If it isn't a big deal, just do a trip to the first destination, then one to the next, and so on. If you're not all going to be using the same waypoints or you are not going to wait for each other at each waypoint before continuing on, then you may just want to set Waze to the final destination and share that and then put Waze in the background while using another program to navigate through the waypoints. That will mean your time to reach the destination will change whenever you go another route to reach a waypoint, but once everyone is on the final leg of the trip, you'll all have accurate information on when you'll arrive.

And yes, multiple waypoints and pre-planning of routes have both been requested many times and should both be on Waze's To-Do list. No idea when they'd be added, but they probably will be added at some point.

For traveling in such a big group and wanting to see where everyone is in real-time, take a look at Glympse and then especially the groups feature.

Glympse won't give you navigation though.