The drive up and over the High Atlas (towards Ouarzazate) is very scenic, the Kasbah at Ait Ben Haddou is stunning, you can easily spend a few hours there (one of my favourite places in Morocco, yes it is a bit touristy, but then we are tourists!), the Kasbah at Telouet is also very nice. I found there was not a lot to do in Ouarzazate unless you wanted to visit the movie studios.
As previously advised, you would not be able to see everything in a day, if you can spare a night to stay in the area, then you will have a very nice time. If you want to hire a private driver for the whole day, they will charge you between £100-£120 per day in total (for a 7 seater type vehicle), then you have your accommodation costs on top (around £10-£30pp).
For a private day trip to the atlas mountains, expect to pay around £80 for a private driver, you maybe able to get a grand taxi to take you for around £50.
Forget a daytrip to Fes, it is just too far away, if you want to see another place, then head to Essaouira, expect to pay around £90-£100 for a private driver, £60-70 for a grand taxi. You could even take the Supertours coach, which costs around £8 per person each way.
I personally like to book before leaving the UK, but that is personal preference, there are lots of tour companies operating around Jemma el Fna square, try to do a bit of research before leaving so you will not end up with one of the "cowboy companies".
There are lots of camels around Marrakech, you will not have a problem finding them.
Also consider taking a horse drawn carriage around the old medina , it is very nice around sunset.......