Robin's nest in my greenhouse

I have discovered that a robin has made a nest in a small cardboard box on the shelf in my greenhouse, there is normally a robin sitting on the eggs (I managed to see 4 eggs when there was no robin on the nest). They seem happy to ignore me when I water the couple of plants I have in there, there is a pane of glass missing at the back quite high up which seems to give them access and I am making sure that the door is firmly shut at all times so that the local cats don't explore. I have been leaving a small amount of bird seed and water in the greenhouse and I am keeping my distance from the nest so as not to disturb them. Is there anything else I can do or shouldn't do, apart from the obvious of not touching the nest or getting too close. Will they be ok in there with the high temperatures that are possible in the greenhouse? Any advice greatfully received!