Do you have any recommendations on how to treat your child when he is in 'silly' mode? Towards the evening when our son gets tired, he becomes often a bit overexcited, acts less thoughtful, and doesn't listen anymore. Any tips?

Try distracting him, get his attention focused on an activity that is of interest to him. My son enjoys looking at / hearing / anything having to do with aeroplanes. If I find him getting out of hand I will address his attention to a coloring book on aeroplanes.