So. If you're going to disregard our warnings, why do you even bother asking in the first place? We can't stop you from going to that park to have your little fun, but don't come back to us whining on how you got arrested and your guns confiscated by the police on the likely chance that they do come around.
They're not stupid.
So it comes down to this;
What you do is entirely up to you, you're responsible for your own actions at this point considering you claim to be over the age of 18. If you feel that fucking around in a park with replica firearms is worth a tab on your criminal record, by all means. Go at it.