At me and Nina's wedding (back in 2002) we had 150 guests - 142 soul people / 8 relatives / One rule - No kids!
We had Adam & Roger Banks looking after the DJing, along with Marco, Rob Holmes, and Teff. To save the hassle of setting up kit, we hired a 'normal' disco, but told the two guys that they were to simply set the kit up, but not to DJ - They didn't understand, and seeing how the evening was going so well on the dance floor they insisted on having a 'piece of the action'. Completely cleared the floor and were kicked off soon after (They didn't mind)
In this instance, including 'what we do' so much so in our wedding worked well because at that time Nina and I were still out every weekend, seeing the very people that shared our day with us. First dance was 'Al Wilson - Show and Tell', then 'the signal' to fill the floor straight after was 'Jackie Wilson - Because Of You'......We cut the cake to 'Isaac Hayes - Shaft'
But - Had our wedding been more of a ratio of 'normal' people, I wouldn't have dreamed of mixing the two. Maybe getting a few played later to appease, but that would be about it. Same with Birthday's, if lot's of 'normals' are there, it's not fair to force our stuff on em - The party is the important thing!
All the best,
Len