change from Fahrenheit to Celsius.

We are doing our children a dis service, teaching them measurements that are not universally understood.
The Fahrenheit scale was the primary temperature standard for climatic, industrial and medical purposes in most English-speaking countries until the 1960s. In the late 1960's and 1970's, the Celsius (formerly centigrade) scale was adopted by most of these countries as part of the standardizing process called metrication.
Only in the United States and a few other countries does the Fahrenheit system continue to be used, and only for non-scientific use. Most other countries have adopted Celsius as the primary scale in all use.