Travel
The wedding will be held at 200 Nashoba Road, Concord, MA 01742. Guests are encouraged to park along the street - plenty of street parking is available, and the street's residents are aware there's a wedding. The house is at the top of the hill at the corner of Nashoba and Garland - look for the white balloons.
Driving:
200 Nashoba Road is right off of Route 2, about 30-45 minutes west of Boston by car.
Train:
The Fitchburg Commuter Rail runs from Boston to Concord, and stops at both North Station and Porter Square in Boston. The train station is a mile from the house, so you'd need to arrange pickup from there. The last train on Saturdays is 9:50 PM.
Uber:
You should also be able to easily call an Uber from Boston/Cambridge/Somerville for around $40-75. Getting from Concord back to Boston is a little harder - Concord is in the suburbs, so Ubers there are scarcer. You might end up having to wait a while to find one, or carpool with other guests from the wedding.