Sounds like your going to have a fun summer! Always great to watch "new" people learning.
Watch some You Tube wakeboarding beginner tip videos.
The ballasts will increase the size of the wake. This may intimidate some beginners. You can also change the wake with speed and the length or the rope. I'd recommend a slower speed and longer rope for the beginners. No reason for them to start out trying to clear the wake, they can "learn" on just one side till they are ready to shorten the rope and speed up to clear the wake.
I doubt removing the fins is a good idea.