I was there last year for ESPN Weekend. The crowd wasn't that bad at all, and it should be OK again this year...usually early March isn't that bad.
Being that I've only been to one, I don't know if any events will be the same as last year. You'll have to check as it gets closer. They had live Q&A sessions with athletes. One they had last year was with Jerry Rice and Tony Gonzalez. To see an alltime legend like Rice in person like that was really cool. They had other Q&A sessions as well (I forget which athletes were there though). They also had several live shows being filmed out there on the stage under the big Fantasia hat. I remember Baseball Tonight being filmed. They'll also have stations set up for autographs and pics with the athletes.
They also had a section set up for competitions - free throw shooting, hockey slap shots, pitching MPH, etc. - where the winners got prizes. All sorts of other cool interactive things as well.
I really enjoyed it and will definitely be back again this year.