Its been a long time since I was at wimbledon, I was fully mobile back then. But if memeory serves me well the outer courts were fairly accessable depending on which day you are there. Obviously if you are in a wheelchair area on one of the show courts it will be accessible anyway.
I never had a problem using a camera or taking one in, but make sure any flash is turned off, they will throw you out if you cause a problem with it.
I always used to take a bottle of champagne, or two, with me in a cool box and lots of sandwiches, as the on site catering is a complete rip off. Never had a problem with any of that either, and they do search any bags on the way in.
Link below provides more info and maps etc
http://www.wimbledon.org/en_GB/about/tickets/guide.htmlI hope you thoroughly enjoy it, its a great day out so long as it dosn't rain too much.