Multisite Domain SEO Advice Needed

Hi

I hope you can assist.

I have a multisite install.

I have an old and well established domain http://capeholidays.info where we rent out holiday homes in Cape Town.

We want to establish an exclusive website listing high value villas in Cape Town.

I want a dedicated theme for these high value villas but I would like to keep the SEO position of my http://capeholidays.info

I can create a new site under a new domain and have none of the old site’s SEO.

I can create a site http://exclusive.capeholidays.info but I am not sure if this will give me any of the SEO from CapeHolidays.

Do you have any ideas how best to do this?