I went to a Mets game at Shea back in September when they completely lost their 6 1/2 game win advantage. I'm pretty sure "professional" grade equipment isn't allowed, but if you can get past the bag check, you should obviously be fine. My suggestion would be to bring your camera and lens, unmounted, in a regular backpack or shoulder bag or something, nothing that looks like a camera bag. Most people don't understand the idea that you can remove a lens on an SLR, so if they're seen separately, he might not think much of it. I did that and also arrived at the game during the peak crowd so the checks did seem a bit rushed. You should be fine though as long as you don't try and stick out like a jerk. 
By the way, I wouldn't worry about the 70-200 4.0 being too slow. It's more likely to be a bit short, even on a 30D, dependent upon where you're sitting. Just be ready to crop A LOT unless you have really stellar seats.