They can start with asking simple math questions and going on to harder questions, as the child gets older. Parents should continually ask children mathematical computation questions and give positive feedback when they respond. Children love to receive positive feedback and that encourages continues growth.
Get in the Kitchen! I was very hesitant for a while with my son when it came to the kitchen. I worried about the GIANT mess that would be left when he was done "helping". You don't even have to take on the entire project with them! You can start small and let your child help with measuring certain ingredients. You can modify the difficulty of the 'lesson' by talking about the different kinds of measuring cups and seeing what other measurements can also add up to equal one cup, etc.
At the end of all levels, children are greeted by a celebration and encouraged by a computer voice to change topics.
As children become more confident in their math skills, give them worksheets one grade level above their current grade. Help them if necessary, but when students become successful in the upper level workbooks; their confidence will really improve. The seed will be planted early and parents can watch as it grows.