Avoid Broadway for the parade, unless you like crowds. The sidewalks are not wide and it's pretty much impassable for hours before and after. Look into Thomas Park (between Broadway and G St.) It'll still be a bit crowded, but the park is a hill with the parade route going in a circle around it. Best view, IMHO. Parking will be a nightmare anywhere you go, so best of luck. I strongly recommend the T.
If you will be into drinking festivities, you will want to find an Irish bar you like early and stay there. It is not a day/night to expect to bar hop the Irish places. BU is not in session, but I think most of the colleges are, so it will be crazy.
looks like we're staying at the Embassy Suites near Logan and taking the train in. [/quote]
I would strongly recommend reconsidering if you can find another hotel for not too much more.
1) You will need to take a shuttle bus to the blue line station (or terminal to catch the silver line), then from there likely transfer to another line since the blue and silver lines only go to the center of downtown and not back bay or other neighborhoods
2) The T only runs until around midnight. Taking a cab back to the hotel can be pricey ($30+) due to a hefty tunnel toll.
3) Nothing within walking distance (which you probably already knew)
EDIT: You *might* be able to walk to the blue line, but I'm not 100% sure