i've just got back from the 10 day trip and am still recovering!
it's HECTIC!! you'll be glad if you get an hour in your hotel room to relax. having said that, it's exciting and always interesting. don't know who your tour manager is but we had daniel and he was fab. you'll feel very well looked after if you have him and it will certainly be a good laugh.
the meals are more than ample. western style buffet brekkie, and lunch and dinner the same size: you all sit on a circular table and dishes are brought out for you to help yourself from. i never felt hungry at all (and i'm a veggie, so it was a little more difficult, but not much).
the loos are a bit grim in a lot of places. i learnt quickly how to use the squat loos: you don't have to squat completely, just bend your legs a little and aim well! take loo roll wherever you go, and hand wipes, although there are taps in all loos. the floors tend to be very slippy and the western-style loos are often very cramped, so much so that it's difficult to get up and down.
there are LOTS OF STEPS to negotiate, often quite sheer and with no handrails.
you often don't get a great deal of time in one place, so always head to the main attraction (temple etc) and then look at things on your way back to the coach, otherwise you might find yourself late.
ALWAYS HAGGLE. it's boring, but everyone expects you to, and you'll prob get something marked at 100 yuan for 10 or under. i found this tedious. make up your mind what you are prepared to pay, tap it into the calculator the vendor presents to you and then haggle for a minute and then walk away shaking your head. they'll run after you and you'll get the thing at the price you want.
take a travel pillow. you're on the go all the time and you may need to kip when you can. i found it invaluable.
take advantage of your chance to go to the supermarket in chengde. this is the first time you'll really have any spare time, and it's an interesting place in itself! you can stock up on odd looking food and sweets to take home.
the great wall. there's the difficult bit and the bloody difficult bit (daniel). i tried the bloody difficult bit (less tourists) and nearly managed it, despite being on crutches! it gets very sheer and difficult to climb (and even more difficult to get down). it'll be difficult if you get vertigo.
take a little electronic fan with you if going when hot. i couldn't have done without mine. batteries are cheap in china.
right, that's all i can think of at the mo. hope it helps. ask any questions if you need to, and i know you'll have a brill time!