Welcome to the Forum, @paul_898!
I’m just guessing with my answers because of the way Video Doorbell v2 works with more than one option. I haven’t seen a definitive answer here or in the Reddit AMA when I skimmed that.

Can the doorbell when pressed also send an alert to the cameras so we know someone is at the door?
I’m not sure what you mean by “send an alert to the cameras”, but if you have compatible cameras already, then you could enable the “Cameras as chime” feature:

The unboxing video illustrates this latter point , which I really like.

Can I order extra chimes?
Not yet, but perhaps by sometime in December, according to the Reddit AMA.