So good that you mentioned the age of the honored birthday person, since the music would need to be tailored to that. If the party is for someone in the U.S.A. that would also make a difference. Find out if they have an ancestry from a foreign country and if so they would probably appreciate some music from there. Otherwise, I would say waltzes are very useful, and operetta music by Gilbert and Sullivan, Lehar, etc. All uplifting.