Hi
Dont worry too much about the mites, they are probably spider mites
http://www.wormcity.co.uk/wormfaq.htm#spidermites and they do like wet conditions.
Make sure you mix in lots of shredded paper or cardboard, this will not only dry the mixture out, but will also add air pockets into the mixture, which will keep your worms happy.
If its really wet, open the lid and let it dry out a little (remember to replace it at the end of the day !)
Also think about what goes in. Fruits and veg with high water content (like tomato and cucumber) will have more water than veg peelings
Hope that has helped
Ronnie