Sorry, this is not an answer to your question. But . . . how would you feel if you apply ED to Dartmouth, get deferred, apply ED2 to CMC, and then get accepted to Dartmouth? A game theory approach to improving your odds of entry is not necessarily best to guide ED decisions.
If you are really indifferent between the 3 schools your approach could make sense. But I’d suggest doing everything you can to learn more about the schools, figuring out which is really best for you and then acting accordingly. ED2 may only make sense if you’re rejected ED1.