One place that isn't very far out of the way on your way back from the meet is:
which reportedly has quite fine lobster rolls. I've had other options there, and I've been quite pleased.
The place that has been rated (my my local lobster roll expert) as among the best anywhere (and the best in NH) is, IIRC, in Meredith NH, which is more of a detour. But I'm not sure where it is. I thought it was this place:
but I don't see lobster roll on their menu.