I'd say 'bad idea' to completely waive the entrance fee. Set all parks to $1 per carload would be a better choice.
As the article mentions, people will care a bit more if they "have some skin in the game".
TT 2015 19RD "TheJayco"
TV 2003 F-350 "Montblanc" - Housebroken chore truck
Sitting in The Cheap Seats.
And proud of it!