Why not do a Beaver Yell to get them going? If you call River Banks (Beavers stand in two straight lines opposite each other, Leaders one at each end if poss ) then Build a Dam (Beavers move out into a circle with Leader(s) in as well. Beavers and Leaders then yell out
123 who are we
we are beavers can't you see
B E A V E R
Beavers, Beavers, RA RA RA.
Beavers could be crouched down and then jump up at the RA RA RA bit and clap their hands behind their backs (to simulate tail slap)
This wakes them up, you can be as loud or as quiet as you like (I think the louder the better!) and then when they have finished they are ready to start their evening off with a game or an activity. The advantage to River Banks and Build a Dam is that you can add new Beavers easily.