To wake Tink you make sure you are at the rope to Fantasyland, going first through the Castle to the rope. From there you can see the shop called Tinkerbell's Treasures. There may be other parents there too with the same idea but at rope drop go directly to the shop and ask if your child can wake her. When we were there a few weeks ago now, on our first day we saw two familys rush for the shop with their child each in a stroller. I hope they they shared the duty, and if it were my child I wouldn't even tell them about it unless it's offered to him/her.
Good luck!