We took two tours to the glacier- mini-trekking and the todos glaciers boat cruise. Skip the cruise- do the trekking.
I am sure big ice is wonderful also, but mini-trekking really covered all the highlights. You get to spend enough time walking on the glacier to enjoy it, and not get exhausted. The bus also takes you to a vista where you get to see how enormous the glacier is.
Skip the todos glaciers boat tour unless you are not in good enough health to do the mini trekking. The mini trekking actually offered better views of the glacier, and the boat tour really was only for older travelers who cannot climb the glacier. Mini-trekking was not very exhausting, so as long as you have no disabilities, you will be fine.
Two full days in el calafate is perfect. you can go mini trekking and then go to an estancia on day.