Essaouira in Morocco is fantastic - beachy and relaxing, less hectic than Marrakech. Also look into Turkey, it's the most family-friendly place you will ever go to, they absolutely adore children there. We went to an area called Datca near Dalaman, quite a long transfer from the airport, but absolutely beautiful. We booked through Anatolian Sky - call them and they can recommend the child-friendly hotels to you.