For a charger around $100, I wold buy the hitec x2 ac plus. It can charge 2 batteries at a time, 100 watts on each in dc mode, so it should charge smaller batteries fairly quickly. I have also heard good things about the icharger 106B, but I think that can only do one battery at a time. I am not sure what size batteries you plan to charge, but if they are fairly small, then the hitec x4 80 might be a better choice, It is a bit more than $100 though. I myself just ordered a hitec x2 ac plus, it should come within a few days.
As far as the batteries go, you could probably get some decent lipos for less than $40 each. If the trucks are lipo ready, than that might be a better option. Make sure that the lipos are treated properly, because they can become dangerous if mistreated. Nimhs wont give you the same performance, but they will work fine. Lipos can be charged faster than nimhs, so they pretty much have a advantage everywhere over nimhs.
Hope that helps, Hubert