Neither be ye idolaters (mēde eidōlolatrai ginesthe). Literally, stop becoming idolaters, implying that some of them had already begun to be. The word eidōlolatrēs seems to be a Christian formation to describe the Christian view. Eating ta eidōlothuta might become a stepping-stone to idolatry in some instances.
Drink (pein). Short form for piein, sometimes even pin occurs (Robertson, Grammar, p. 204).
To play (paizein). This old verb to play like a child occurs nowhere else in the N.T., but is common in the lxx and it is quoted here from Ex 32:6. In idolatrous festivals like that witnessed by Moses when he saw the people singing and dancing around the golden calf (Exo 32:18.).