Where to install wordpress?

Hello there,

I need to create a website that shows an html static page as the homepage (Example: http://www.example.com). This page will act as a splash page and will redirect users to the site of their choice (Cats Site and Dogs Site). Those sites will show at http://www.example.com/cats and http://www.example.com/dogs respectively. So when an user lands in http://www.domesticanimals.com/cats for example, they will see the homepage for the Cats Site. The dogs site will be an ecomerce website down the road, so I prefer to just make a fresh installation of wordpress at http://www.example.com/dogs.

That being said, how will it be better to set up the Cats Site and the static html page?
Should I install wordpress on the root or the “cats” sub-directory? My initial thought was to install wordpress on the Cats sub-directory, have the front-page show the homepage, and create a page template for the static html page that needs to display at http://www.example.com…but how do I do this last task and is it a SEO friendly practice?

Any suggestions on how I can set this “Cats” site up would be greatly appreciated!

Ximereds