Benefit of linked site versus embedded pages

This may sound obvious but:
Im building a site which is acting collectively for three separate B&Bs.

The client wants an overview page and then links to the 3 individual sites.

Is a one page web site weak in terms of search engine activity and would i therefore be better to copy into this new site all the pages from the three individual sites?

The single page probably wouldn’t add much value - I’d say spend the extra time improving the three separate sites.