Muss-ed has told you how to get to the chatel bike park which is in fact in pre la joux. Chatel itself has a couple of dh trails and is reached from the bottom of the bike park by bus. The bus stops for lunch though so check times before you head out there. First Super morzine lift and a direct run will have you comfortably on the bus from memory.
The chatel bike park has a load of trails of different grades and is pretty good. The tracks over at les crosets are worth a visit too and you get to have the fun of the puncture alley or gr5 return that way too.
The trails outside of les gets/morzine themselves require a little pedalling to reach (and i do mean a little) but are a lot quieter for it, a good weekend choice when morzine can be heaving.
Les gets and morzine both have new trails for this year, it’s difficult to grade trails by resort as all tend to have a mix. reds are fine and most of the blacks will be too.
have fun, i’m out there for a week in august.