Zumstein (or something like that) is cool, well was 30 odd years ago when I was there last.
There's a good one in hall's gap but can't think of the name.
No camping at Zumsteins these days...
...... Day visits only now.
Haven't used any of the CP's there for a few years, so can't offer any recommendations.
The Grampians isn't a huge area. "Several days" would give plenty of time to see the main attractions.
McKenzie Falls is very nice, but a very steep walk down to the base.