We don't have our ECS yet, but we'll bring one home in mid October.
What I want to say is based on my experience with our current dog. Make sure you decide upon some rules and stick with them. For instance, if you find later on that you are not happy with the dog sleeping in your bed, will have a much harder time training him to sleep on his mattress than if you did it from the beginning.
In time I realized that I cannot sleep with our dog in bed (allergy and sleeping issues) and now she seems very depressed just because I put her mattress on the ground. I wish she has never gotten used in our bed and now I would not feel so guilty that she is sad.
Just my experience with our dog.
Good luck!