Hi Charee,
I've always thought Edward Norton should play John Phillips, Charize (don't know if I spelled that correctly) Theron could play Michelle Phillips, Nicky Blonsky or that girl from the Hairspray musical could play Cass Elliot. Sorry, I can never remember her name, and the actor who plays Carlisle in the Twilight movies could play Denny Doherty. Sorry, I can't remeber his name either. Bijou playing Michelle is an interesting choice, though.
Take care,
Nicole