My mom and I always tie and always use yarn. Use baby yarn for baby quilts. double knot. My 32 year old niece asked my mom to finally but a new back on a quilt mom made when she was a baby. We always make them at least WOF X a yard and a half.
We have never had a problem or even a tie come out and the quilts are used. I got mad at my son for using a special one mom had given him. He informed me he was honoring mom by using it!! I KNOW he is right.
We have a frame like thing dad made to stretch it on. We tie at least every 6 inches as fits the pattern. We use polyester batting from Oklee Quilt company. We once threw a piece in the wash with no outside or tieing. Through sever washes it never even changed shape. It works for us