How about you let other people take your child to the playgroup? My boy "sticks" with me a lot and he really likes crying. When my boy attended PN for the first day, I accompanied him and he cried a lot. He just wanted to stay with me and cannot be apart from me. The 2nd day I let my maid accompany him. He did not bother to cry at all.
When he attended other interest class for the first day, I let my mom and the maid take him to the class. He did not cry at all.