World_end_soon, even if you search these forums - you will not find an exact answer to your questions or worries.
There are a few things you can do:
- Do everything with reason
- Check what other similar (unpunished) site set-ups do
Many, many sites have reciproc. links. They form natural ways of helping each other and the visitor and they show a form of a community.
As starters, I would say the best way to do it is as you described. Do not let the linking point to each others same page.
More importantly, let each site earn its own incoming links from different sites and let each site link out to different other sites.
As a guess, I would make sure that for every link pointing to my own sites
from my own sites, I would link out a six-fold of links to other independant sites. Same goes for independant back-links.