Robin Nest

I have a nest with eggs in a small tool holder at my allotment.  There's a small gap for the adult robins to get in and out but I just want to check the young will be able leave safely.  They need to fly up from the nest and out of a gap about 5cm high.  The rest of the the container is full of tools and netting, not ideal for any bird.  I have taken out what I can without disturbing the nest and can cover the netting etc  in blankets if that would help? The robin knows me as I feed it but I don't want to scare it either.  Thank you for any advice.