Here's another idea - if you want 5 minutes peace (exactly 5 minutes that is), set a stopwatch for 5 minutes and sit your kids next to a window overlooking a road. Get them to fill in a tally chart that records the colours of the different cars that drive past. If they're up for it they can then make this into a bar chart. They might need your help for this bit, depending on their ages - this is why it's only 5 minutes of peace. Mine actually co-operated on this one, and worked together to spot and record the numbers of cars driving past. I have no idea how accurate their recording was, but did that really matter? Probably not.
You can adapt these to older kids too. Draw Venn diagrams on a piece of paper and write in the objects, or names, if hula hoops and toys are too babyish. Make it more difficult by adding another circle and labelling them with things that interest them: Names of x-factor, big brother and BGT contestants, or whatever they're into. They could do a survey among friends and family of favourite types of TV programmes, or music, or hair colour, or time spent on the internet every day! Then ask them to present the results in an appropriate type of chart. Play "I spy a shape" with more points for more unusual shapes. E.g. 1 point for a circle or square, 3 points for an oval, 5 points for a hexagon or pentagon.
I think Maths is fun and my kids love these kind of challenges. My only problem is the time it takes to tidy up after a Maths day - now where did they get that blue sleeping bag from?