Ideas for encouraging DS to exercise

[ceeveebee]

I have 5 yo b/g twins. DD never sits still and is always running, jumping, loves going on her scooter or bike, loves gymnastics and PE.
But DS really doesn't like exercise of any form - moans when we go for a walk, won't run for more than 5 yards, won't join in at PE etc. I know all children are different and if he's just not interest in sport, that's fine, but I do want him to be healthy.
He's been going to a preschool football class on Saturday mornings for a few months which he did seem to enjoy but now they've made him go into the next group for age 5-7 which is outdoors and he just refused to join in yesterday, just kept crying and running to me telling me how much he hates football. He just wants to play with Lego or watch TV.
Does anyone have any ideas of ways to gently encourage without making a big issue?
Walking to school is not really an option most days as I work full time so drop them on my way in (I'd be late otherwise).
Thanks