1. It is OK to list pets, just list family too. I plan on having my pets listed.
2. Write up the obituary before the person passes or write your own and keep it updated. It is so much easier then than at the time of passing when every ones emotions are going every which way.
It is fine to keep it short but make sure you add the basic information such as dates and places of deaths and births and parents and childrens names. It is amazing how such a little thing can be so important to future generations.