Just me personally... but this is SOOO tacky and overrated. But, she's your girl and not me so I'm just throwing that out there as a female. Memorable doesn't always mean flashy and splashy.
I would probably contact the Fenway Park and this article might help too:
http://sports.weddings.com/articles/...nway-park.aspx
The article provides a phone number (be sure to ask for Fan Services and Entertaiment Department) and states that a $250 fee (based on 2009 rates) may apply.