Hi, sir. I am afraid that the bus driver will not wait for you if you want to have a visit of Huanglong scenic and historic area. Well, after visiting the scenic area, you could catch another shuttle bus to Jiuzhaigou at Huanglong.
You can lock your luggage at the ticket office of Huanglong scenic spot.

Although Sally says the bus driver will not wait, according to tip 3 for the shuttle bus above on this Web page, "The bus will wait for the passengers at Huanglong if needed, and then continues to run to the Jiuzhaigou". Could you please explain yourself? Or is there perhaps a minimum of passangers for the bus to wait?

Thank you

I think Sally just has said one profile of the shuttle bus. In fact, upon arrive at Jiuhuang Airport, you will find two kinds of shuttle bus. One will run from the Airport to Jiuzhaigou Airport, and the other will run on the itinerary of Airport->Huanglong->Jiuzhaigou. By the latter one, the driver will wait for you at Huanglong.
Ps: If only few of passengers on your flight would like to visit Huanglong, you have to wait for a while at the airport until the van is filled. On the other hand, you may consider sharing a cab with others to Huanglong and then Jiuzhaigou. Cab could be hire easily upon arrive at the airport.