I would drive the 60+ miles to the Bronx Zoo when my kids were little. Still one of the best zoos in the nation. This was pre internet days and I would call before scheduling to find out which days were FREE. Then I would schedule any weekdays EXCEPT those free days. I like my animals IN CAGES, not wandering around with the populace.
Having gone to school within walkin distance of the Bronx zoo, it was usually empty on free days as it was usually on a Wednesday if I recall. The funny thing is that none of the feral youth would ever think of settin foot in the NY Botanical Garden on free days, preferring instead to head up to Westchester or Manhattan when they cut class.