We have successfully configured the multi-sites in EPiserver 7 version and it's working fine.

After creating the two different website the names are displayed in the top website preview menu (Please refer the screenshot below)

Problem scenario:

We are selecting child page under the start page in the tree and we want to view the child page in preview mode. But, when we click the display menu (as attached above) it shows the start page in the preview mode instead of showing the current selected page. So is there any way to preview the current page before publishing the page like the single website functionality or anybody have the idea to fix this problem.