Whenever I do an upgrade around here, I just take the existing meters out, and put them back into the corresponding new sockets. You just have to be careful not to mix them up, or there will be a lot of confusion when everyone's bills come in.
When dealing with more than one meter, I usually mark them right on the glass dome with a sharpie marker before pulling them.
You are going to need the PoCo to provide you with the new meters for the house panels, right? So why not ask when you call them to arrange for the new meters?