i'd agree with what berkeley mike had to say above. i've taken my wife and son in there a bunch of times. with my wife we stay along the shoreline which is flatter and easier. not that doing a full loop up and around is really hard but there are technical sections which are tricky and can be a bit scary (big dropoffs down the slope) for beginners. also if you go during primetime there's a decent amount of traffic which can also be cumbersome for a beginner.
have fun, it's the best trail i know of for beginners. would love to find more, almost everything in the bay area involves decent climbing which seperates skill and age levels...