Selecting existing child post when creating a new parent post.

Hi, I have three customs post-types – Events, Organisers and Venues. I'm using Events as the intermediary post-type, i.e. it is the parent to both Organisers and Venues. When creating a new Event I can create new child post-types but what I want is to select existing child posts i.e. existing organiser or venue. Is this possible?

Cheers, Mark