Of all the DGC we have looked after, our Grandson was the hardest to get down for a nap after lunch, no matter how active he had been during the morning. I resorted to putting him in our pushchair in the lie-back position, with a blanket over him, and walking round the block (sometimes further!) He liked to be out and gradually relaxed into sleep. I would push him into a quiet room when we got home. If I attempted to get him out, he would wake up.
With weather like today, I used to put the rain-covers on the pushchair and brave the elements.
Luckily I like to walk.