I just love fairies! I think I was the MOST excited to meet Tinker Bell when my family and I stopped by for a little fairy love.
If your little ones want to meet Tink, Rosetta, Fawn, Silvermist, and all the rest of the fairies, then you need to stop in to Adventureland for autographs and hugs.
I've found that the wait gets longer as the day goes on, so if meeting Tink is a "must-do" you need to add it into your schedule earlier in your day. The good news is that you wait in the air-conditioning as opposed to outside for many of the other meets. There are also short Tinker Bell Movie clips that play while you wait, making it a little less boring of a wait.
You never know exactly which characters EXCEPT for Tinker Bell. She will ALWAYS be present for your greeting. It could be any of the others, however. I would suggest asking any of the "character handlers" if they know who else will be out and when if you miss one of the fairies you were looking forward to seeing.
To meet the Fairies at Magic Kingdom look directly to your RIGHT when you cross the bridge into Adventureland. Its kind of easy to miss as there is just a sign out there that reads the wait time and it doesn't really stand out. So make sure you keep your eyes peeled! And tell Tink HEY for me!