Woodland outdoor microscopy advice
1: Yes it is possible

2: It's not as easy as lab conditions because of variable conditions, chances of equipment breaking, especially when small children are involved. 

3: You can also look at a Foldscope. Its a small, but powerful microscope made with paper. It was developed by a scientist called Manu Prakash, and although it is still in its beta testing stage, I'm sure you would be able to obtain a few for your students. It is incredibly cheap, very customizable and really user friendly. 

P.S.: With the amount I endorse the Foldscope, you would have thought they could have shipped one of the damn things to India for me.