What is the temperature in Beijing in the early May and any suggestions on the places to go?

Hi! My family and I are planning a trip to Beijing this May 1st and will be staying there for six days. Since it will be spring at that time do you suggest we still bring winter coats and boots in case it gets cold? and can you please give a list of places we can go to suppose we have a three yr. old kid with us. Is it still ideal to be going to the great wall or the forbidden city even with frequent sandstorms during this time? hope you reply.. thanks!