Dressy Casual Guys- no jeans but also no need for a suit jacket if you don't want to wear one Gals- fun casual dresses The ceremony and parts of the reception will be on grass!
Your invitation and the RSVP page will include a guest if you can bring a plus 1.
If they are included on your RSVP then yep! There's even a playground down the hill from the reception area for them to play on. Please make sure there is an adult with them at all times.
There will be no transportation from the park to the hotels but it should be pretty easy to get uber/lyft. There's also plenty of parking.
We would recommend hotels in Fishkill. There are also some nice airbnbs in the area.