Of course it takes some time for the Earth to warm up or cool down. The oceans make a big contribution to delaying the heating or cooling of the Earth. In the summer, it is often cooler at the sea cost, and winters along the coasts are milder than further inland. Hopefully, they will begin to think about the atmosphere. If not, ask if the Moon s surface could get as cold as empty space.
Many factors combine to make life on the Earth habitable for all of the species which live here.
Even though seasons change, the temperatures are still within a range we can handle, and life has adapted to this planet. Just by observing the world around us and using the tools of Scientific Inquiry.