Sorry you didn't get the answers you were looking for. I've never been to progressive. I have been to Fenway, but it looks like you went yesterday. Citi is one of my hometown parks. I haven't tried to get anything autographed since I was a kid, and I'm sure with the New Citifield and Yankee stadiums it's different now. However, unless you're getting him jerseys in adult sizes, I wouldn't get a jersey for him. So I would go with the baseballs. Some people collect the mini bats, we collect the ice cream helmets.
Hope you're having a good time this weekend!