On object avoidance: fairly easy, once you have the lejos-specific java down. Just a pair of bumpers and a pair of motors, and you're good to go. There are a large number of tutorials available for that portion of your project, and I'd tackle that as a first step. It'll also give you a sense of the bots themselves.
As for communication protocols, they do exist, although I haven't used them myself yet.
You'll also have to use some of the data-saving portions of the lejos stuff, which I haven't delved into either.
Good luck! Your project sounds fascinating, and I hope to hear how it works out for you.
"The end is important in all things." - Yamamoto Tsunetomo