Problems that have already occured before shooting

We have recently been told by one of our actors, who we were meant to be using in a few weeks is pregnant. it would be extremely unsafe to use her in our movie, as our actors are expected to be running around in a forest and getting in and out very quickly of a tent. However, we have already found a new, even better actor who is already good friends with our others actors which should make the acting look more realistic. We still plan to be shooing on the same day and have already checked that all 3 actors are available on the same day. Although, me and Imogen are still not sure on the 3rd actor and as our storyline keeps changing the actor we had in mind may not be appropriate. However, our other two are very well suited and they are Liam Stainbys and Emma Dixon.