My question is how to maintain and optimize SEO when moving a site from the domain root to a subfolder, creating a second parallel subfolder, and having the domain root be a landing page that allows users to choose between the two subfolders.

Hopefully a (fake) example will illustrate my question best. Imagine the website for a small local business that serves its surrounding neighborhood -- let's call it ACME Cleaners of Crown Heights. Crown Heights is the neighborhood. The URL is www.acmecleaners.com. This site has good SEO and does well for searches looking the cleaning services in the Crown Heights area.

Now the business has expanded to a second location in a different neighborhood, let's call it East End. The new location is called ACME Cleaners of East End.

As for the website, the homepage, www.acmecleaners.com, which used to be the homepage for the Crown Heights location, has been changed to a landing page that simply shows the ACME Cleaners logo and gives the user a choice between the two locations. The user is then taken to either www.acmecleaners.com/crown-heights or www.acmecleaners.com/east-end, which are individual WordPress sites for each location. Via a cookie, users are redirectly directly to the individual location site next time they visit www.acmecleaners.com.

Specific questions:

1. What should I keep in mind to maintain the strong SEO that the Crown Heights location had now that its site is moving from www.acmecleaners.com to www.acmecleaners.com/crown-heights?

2. Specifically, how do I "tell" Google that the right URL for searches for "cleaning in Crown Heights" is now www.acmecleaners.com/crown-heights, not the domain root?

3. Likewise, what do I do to get searches for "cleaning services in East End" to show www.acmecleaners.com/east-end? Interestingly, without me doing anything, this search is already generating first-page results for pages within the subfolder, e.g. www.acmecleaners.com/east-end/about-us, but not for the location "homepage" which is simply www.acmecleaners.com/east-end.

4. What SEO should I do for the new landing page at www.acmecleaners.com to support good SEO for both store locations/website subfolders?

5. Any other do's and don't do's in this situation?