I run disco birthday parties in Melbourne so I can't get you to come to my venue but I have HEAPS of tips for disco parties.
First up put out some disco colouring in sheets & coloured pens on a table so when the kids get tired, or if they're initially shy they have something they love to do. There are heaps you can print straight off the net. Basically that will take care of the first 30mins of your party. Use your garage because it's easy to make dark or close the curtains in a playroom. Disco lights are really cheap at KMart, $10 or under, you only need 1 or 2. If you have sing star or even pretend microphones (look in the $2 shops) the kids will feel like pop stars.
You'll only need a few games because they'll be dancing and singing and making their own fun. For Limbo you can just use a broom handle with a feather boa wrapped around it or even a skipping rope (there is always 1 or 2 kids who want to help hold the limbo pole instead of joining in so you'll have helpers).
Musical statues is a favourite and at 6yrs I'd do a pass the parcel. You don't have to wrap the prizes, have a pretty bag they dip their hands into (no mess!)
Make sure you have drinks on hand throughout the party as dancing is thirsty work. Keep the food simple. Fairy bread, chips, lollies, fruit platter, party pies/sausage roills. You're all done!
I'm sure whatever you do you'll have a great party