There are a lot of good online resources with lists of popular dance music. The trick is finding the music legally, since it's a Church dance (and they likely won't have a budget).
Just search for "best DJ songs" and you'll find plenty of lists online.
As for actually playing the music, your best bet is to play 3 fast songs, then a slow song. Especially if you can group them by theme (3 fast 80s songs, then a slow 80s song, then 3 fast 90s songs, then a slow 90s song, three fast disco songs, then a slow 70s song, three fast country songs, then a slow country song, etc.)
I DJ'd for 10 years, and this was usually the best way to go for parties with people from "different generations".
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