I saw a supernanny episode where they set up a system for the kids to help with the chores... I don't remember it exactly, so this could be totally different..
First I would set the kids down and 'brainstorm' with them about what needs done daily/weekly around the house. This gets them into the mind-set that they helped pick out what needs done so it doesnt seem like you're forcing them as much.. Make the brainstorming fun, when they can't think of anything, suggest stuff- "Do we stuff all the towels in the closet? No? Well, maybe we should put folding laundry on the list? What do you think?" etc.
Split that list into two parts: things each child has to do daily no matter what, and community stuff that needs done around the house that any one of you can do.
Then write the community chores on different fun paper and cut out. Have the kids help you every step of the way, writing, cutting, decorating, whatever. Get the chores laminated and stick velcro strips on the back. Place in a special container.
Use a scrapbook page for each child and put their name on top. Under the names write their specific daily/weekly chores and check mark boxes. Lamanate these pages for strength. Put the opposing velcro tabs on the lower parts of the sheets so the kids can velcro their community chores, making sure to leave room for the random sizes of the chore papers.
Then weekly, or daily have the kids draw for their chores!
IE- each child draws till there are no chores left in the special container and puts those chores on their sheet. suzy has to do dishes this week, tommy vaccuums. You can even make a sheet for yourself to visually show them how much work you do too so it feels like you're all in it together.
As for rewards, i dunno. Just keep it fun and keep that sense of community. :) Good Luck! Hope this helps even a little!