we are planning to go this August to Marrakesh and then Ouazazarte and Agadir. Is it best to rent a car and chance the driving, or take the Grands taxis i have read about?

I travelled all of Morocco with my then 6 year old daughter in November 2006. We had a great time using public transport (mostly trains), but also found for the ong haul days (ex. Fez over the Atlas Mountains to Marrakesh), it was affordable to hire a private driver who was not only english speaking, but took the 8 hour drive to stop us at scenic spots, was able to allow rest stops at places he knew with western bathrroms for my daughter, etc. We never would have been able to get from point to point in one day via public transport. Adn we would never have been able to see the views and vists up in some of the Berber villages that we did had we not hired a public driver.

I would likely not want to make the drive you are suggesting. Maybe consider hiring a driver.

Have a great time though...Morocco was magnificent in every way!