Steam the photos away from their backing. Use a tea kettle, boil the water, turn the flame down low as soon as the steam comes out of the spout. hold the photo still attached to the album approx. 2" from spout, directing the steam to the corner of the photo... as soon as the photo begins to curl away from the the backing, remove it form the steam, using tweezers, gently pull the photo, but don't tug at it when it doesn't want to peel away, return it the steam and repeat the process until the photo completely comes away from the backing. If there is any backing residue on the photo after you've completed the process, return it again to the steam and repeat.
After the photo is "clean", it will looked curled. Wait till the photo is completely dry, then press it between two books, this will flatten it.
Tried and true, works every time!
Good luck.