The closest airport would be Portsmouth Pease International, but the airport has a very limited amount of places it flies to and from. The other airports around would be Boston Logan International and Manchester-Boston Regional Airport.
The parking is free at the Wentworth by the Sea. On the day of the wedding, valet will be free for guest not spending the night. Anyone spending the night, can pay $5 for valet or just park themselves.
If you have any questions, please contact anyone that is in the wedding party, except the bride and groom! The Wentworth by the Sea should be able to answer any questions about the wedding (both ceremony and reception are being held at the same venue). The number to call for the Wentworth by the Sea is (603) 422-7322.