Yes, you can do online check in for both.
Yes, they will store your luggage for you. Call luggage services and advise them of the room change and you should be able to make arrangements for them to move it for you. They should have you leave it by the window (and you will have to advise how many pieces of luggage), they will retrieve it, and then move it to your new room for you. I would ask to talk to a mgr about this when you first check in. This is why I like checking in face to face to address things like this.

I have done similar things there before. I was just at POP earlier this month and had a late check in. My room wasn't where I wanted so after night one, they moved me. So I am super familiar with room changes. It's easy peasy if you let them do the work, just follow their instructions.