Can you set a homepage in Safari?

The only way I know how is "add a home page" and then launch it from your home screen.

No. What you can do is make a web clip of your preferred home page and use that icon to launch Safari. See page 41 of the iPad User Guide.

The easy way is to just go to your main home page and exit. When you start up Safari again, you are where you left off.

You can have multiple browsers on in the browser stack. Click the stack button to see all webpages activated. Keep one for your homepage and use that when you exit each time.