I'd hire a good financial planner, invest most of it so that the interest from our investments would give us a decent income each month, and not change too much about our lifestyle. DH would probably still work. (Not too exciting, I know, but that is honestly what I would do.)
The only splurges I would do would be to pay off our cars, then give each family member a "gift" of $25k or so each. (sisters, parents, etc.)
(oh yah, I would probably take my entire family on a really nice vacation first.)
That's about it.... boring, I know.

Forgot to add: I would go down to the hospital where we had our daughter and give a donation in her name to a family with an infant who was ill, premature, special needs, whatever. (For those who don't know, we had a daughter who was born critically ill, and passed away in my arms only four hours later. But we were blessed with her two healthy younger brothers later.) I know what we went through, and someone shouldn't have to worry about their finances during the scariest moments in their lives. There is enough stress they have to deal with without wondering how dad can afford to be off of work so that he can be by his wife and baby's side. So I would find a family or two and just give them a bunch of money, no obligations whatsoever, and hope that it would lighten their load just a little.
SORRY SO LONG!