There's even a tutorial for how to make a light up dance floor, wouldn't that be neat? Of course that would probably be more of an at home project but I thought I'd include it anyway. Dance lights should be provided by the DJ but it case they are not you can find a lot of different colored flashing light apparatuses online.
If you really want to go all out with the 70s theme ask your guests to dress up accordingly. Don't forget about yourself. When pictures and/or mass is done and it's time to really party then change into a 70s inspired party dress or even a sequined jumpsuit.




