When will your husband be in Beijing? Hope he will not come across the national holiday. Considering he has only 2 days, i'd like to give you a suggestion like this:
Day one: visit Tiananmen square, forbidden city, summer palace.
Day two: visit the badaling or mutianyu great wall and temple of heaven.
what i list are all the highlights in beijing. if your husband visit during the national holiday, he may need to plan another schedule, as these sites will be crowded with people and traffic to these places will be terrible. it will be hard to access these places. good luck anyway.