If people want to be included they will include themselves...

It depends on what they are doing, or how your interaction starts:
if you're just walking up and starting a conversation it will be pretty hard to include everybody
if you are running up because you need to get a specific task accomplished in a bet with a friend and are full of energy then they are more than likely going to want to be part of it

but as K said do what the situation dictates, he is much better at saying it than me...