I put buttons on a quilt for my DD (adult) a few years ago and there have been no problems with them. I added the buttons as the very last step of making the quilt, after binding. She used it on her bed and it has been washed many times. She got a black lab puppy two years ago, who now sleeps in her bed so she has the quilt folded on the back of a chair. Didn't want to take any chances or have to wash it so frequently as you have to with a fur baby.
Anyway, I say go for the buttons!