Barn owls in the chimney

We have known for three years that there's a resident owl in the unused section of the chimney in our French house - it was the reason the chimney couldn't be capped when a new liner was put in. Sometimes we hear it in the night, and it sounds uncannily like human snoring!
A few weeks ago friends came to visit, and occupied the second bedroom which is now rarely used. There's a fireplace there with a board in front of it. One night the noise kept one of our friends awake, and she decided to investigate. Here's what she found, to our astonishment: two baby barn owls.

Now we have a worry - can they get out, once they fledge, assuming they survive? Will the noise of the roofers climbing about over their heads frighten the parents? Will we be able to let them fly free and, choosing our moment when the mother or father is absent, take advantage of the scaffolding to cap the chimney at last? Can I have life and freedom for these handsome creatures as well as a more guano-free and hygienic bedroom? So much for the delights of French rural life!I'll report on their, and our, progress.