Here are some useful links with information about bees:
Bumblebee identification guide
Bumblebee Conservation Trust resources for schools
Online bumblebee identification
The Hive (formerly Suntrap) in Epping offers a wide range of activities for children of all ages.
The Blue Peter Green Badge has lots of information about pollinators and green issues.
Here are information sheets on what to look for in the playground in April May
You can easily make a bee hotel, either from a 2 pint milk container cut down, or an old mug and bamboo canes.
You can also drill 6-10mm wide holes, 10cm deep in a piece of wood or a old brick.
