You absolutely want to do address this on the new site, not the old one - it's the only way you'll be able to fully transfer the ranking authority form the old site to new.
Since the old home page is almost certainly the strongest on the old site, you may want to consider redirecting it to the new home page, with some referrer-triggered dynamic explanatory text. This could then link to the "about the buyout" page you mentioned for more info. This way, the ranking authority is transferring to a critically important page on the new site, instead of just helping to rank the non-essential about buyout page itself.
Ideally, you're going to want to redirect the pages from the old site to the equivalent URLs on the new one as well. That will provide significantly better authority transfer that just redirecting all pages of the old site to new home page/about buyout page. In which case the same referrer-triggered dynamic content or a header bar can be utilised effectively for those pages as well.
Make sense?
Paul

