But in theory, ID and Evolution could easily coexist.
No, they cannot!
One is knowledge the other is propaganda from a particular christian sect.
Secondly, one could believe that a world was created by an intelligent being, and that creatures evolved since then.
Sure, you can believe the big bang was done by an intelligent being, it's a theory. I don't think it's a good one but we don't exactly know the right answer yet, so in the meantime someone can call it god. There is no reason to believe there is a personal god though and there is enough evidence that we can say the world isn't created in a week and surely not some 1000 years ago.
Also, a day has not always been standardized, assumedly the "7 Days", is not made up of 24 hour days. The way it is written, it likely refers to a period of time only.