C.S.
They understand...so before you leave the house, explain to him tantrums are not acceptable and if he throws one, you will leave the park and he will take a [insert punishment]. Explain to him he has to use words when he is upset and maybe the problem can be fixed.
If you see a sign of a fit, remind him to use his words or he has to leave the park. If he has to leave the park, he has legs, he can walk. Grab him by the back of the pants and an arm and escort him out. Otherwise, what will you do when he weighs 60 lbs?