If you have a. good DJ, then trust them to do the right thing.
But there aren't that many good DJs..... so maybe give some hints and suggestions.
My daughter was at a wedding a few days ago - about 40 guests - the brides contacted all the guests in advance and asked them to choose a song that was special to them. Worked well, depending on style some were played for the dancing, and some were played during the "mingling and photos".
In Scotland, you've got to have a bit of Proclaimers - I was at a wedding recently where they started off with Proclaimers "Let's Get Married", leading straight into "(I want to spend my ) Life With You"