Yes these can all be parts of the same site.
For Plan A if each are individual domains, each will be a parent site and not child.
For Plan B if each are part of the same domain then you can do children.
I have no problem with Google, MSN and Yahoo all spider my sites no problem, I wouldnt worry about it.
Make sure you want to use Godaddy, talk to people who have experience with them, if not then ask for a recomendation.
To do unique domain name A you need to register your domain with a host
if they can do install for you then request it, other wise copy theinstall files, Make sure you edit the web config properly
you browse to the site to initialize installation.
Any questions?