There are loads of free maths games online which make learning maths so much more enjoyable for kids than just staring at an excercise book and they don't really consider it work at all. My six-year old often asks to play them in his freetime and obviously, the more he practices the easier, less frustating and more enjoyable his lessons are so it really pays off. The more he plays, the less he resists more traditional forms of teaching.
I also try to compare learning maths to solving puzzles or clues in a quest, telling him that once he's got the basics, he can break any code. This is less effective and usually involves additional bribary and haribo, but baby steps. Ultimately, you can't go wrong with getting them in front of a screen though (and you can even make dinner in the meantime). Hope some of this helps!