My wife and mother-in-law plan to come to Boston's Logan airport later next month in the morning. They will be picked up by relatives that evening, and stay with them overnight.

They wish to do some sightseeing during the daytime. However, they do not want to rent a car.

What is the most cost-effective way to do the sightseeing? The questions relate to how to go from the airport to downtown in the most cost-effective way, and then do sightseeing on either a sightseeing bus tour, or a hop-on, hop-off bus tour (they would prefer the latter). Finally, could they store their baggage/luggage at the airport, while they went out sightseeing.