That's a good way to start. That way if they are not listening at this new park you leave right away. No big loss and it sets the standard for the strawberry festival.
You want them to really behave at the festival as I imagine you want to be there too. I would NOT tell them that if they are good at the new park that they will go to the festival. Reason is because if they are acting up, then you have to follow through with the no festival consequence.
Save the good feed back for when they are good after being at the new park. This way if they are not good then you can leave right away with them crying asking to stay and no big loss. After that I am sure they will remember that at the strawberry festival.
well you get the idea, good luck
Me late 30's W mid 30's T 15, M 10 S4, S7 ILYBNILWY June 2015 In house S July 2015 W rings off Oct 2015 My ring off Feb 2015 Separate houses June 2016