Somerville's annual Patriots' Day celebration will be held at Foss Park on Monday, April 18 10-11:30 am. There will be a Colonial Fair with games, music by the Somerville High School band, period refreshments, and colonial reenactors. If you play your cards right, you might even get to meet Paul Revere's horse (she has a very busy social schedule; she can't make time for everyone). If you are interested in reenactments of the Battles of Lexington and Concord, the National Park Service has a complete schedule of events here. However, April 18 is also the day of the Boston Marathon, which will affect traffic and MBTA service. So getting around the greater Boston area is going to be quite difficult. You can learn about road and station closures here and here.