If you come the end of April or early May then snow should not be a problem.
I saw that you live in south carolina. I'm not sure where you are but the flights from myrtle beach using spirit air are by far the cheapest. My inlaws live in MB so we fly there all the time.
I would stick with a hotel chain. The sheraton has a nice hotel that is attached to the prudential. It is walking distance to copley and newbury street if you like shopping. The long wharf Marriott right near faneuil hall is nice too.
I would definitely take one night to have dinner in the north end and visit mike's pastries. You must have reservations if you want to eat anywhere in the north end for dinner.
you can get pretty much anywhere with the subway. Just make sure that you check the schedules because some run less frequently or not all all on weekends and holidays.
Unless you want to see the marathon AVOID patriots day weekend in April!!! The city is crazy crowded and you can not get anywhere because of street closings.
I know you said that you were not planning any sports outings but I must admit that redsox games are one of my favorite things to do. Especially if you can get tickets to an afternoon game in the spring.
Visitors | City of Boston
is a good website that has information about the parks and historic sites in the city so you can plan your trip