I also have been looking at cleaning out a pond. Some random thoughts that I have looked at or tried.

Instead of the dumpsters you might also want to look at dewatering bags.

I bought a 3" gas powered trash pump from Northern Tool. http://www.northerntool.com/shop/tools/product_200380031_200380031
It works very well and it is relatively quite cheap.

A couple years ago I had one end of my pond dug out with a large excavator and when I later drained the pond I found the area he dug was very uneven and looked rather terrible. Realizing it's always underwater but I would think it would effect how well my aerator will work on that part of the pond.

For mine the contractor wanted to build a muck retainment area to put the muck in. Basically making a hole for muck storage.

I actually pumped mine dry and the muck is way thicker than I originally thought.

Anyway I'm sure with all the experts here you will get a lot of helpful advise. I know I have learned a ton on here.