Run to each of four corners for a different part of the Beaver Promise
Four posters with the Beaver Promise written in four parts
Make Four Posters with
"Do my best"
Put one up in each corner of the hall and then explain the rules to the Beavers...
Get them to shout "I promise" and then the leader replies with one of the sentences above - they then race to that corner, and the last one is out... they all shout "I promise" again and you send them off to another corner!