I've taught inclusive physical education classes in the past, giving me the opportunity to work with students of various needs all in one classroom.
Some tips that come to mind right away:
- Set small goals. Until you learn the ins and outs of what motivates your child, you will probably experience times where it's difficult to get them to buy in. Small, attainable goals (sometimes with a reward at the end) are a good way to build up the intrinsic motivation.
- Relate fitness to something your kid already loves. This goes along with the incentive and rewards idea. They aren't necessarily earning something every time they succeed, but come up with ways to relate working out to things that already are super "cool" in their mind.
- Consider starting with the locomotor skills before you dive into more challenging fitness concepts- running, jumping, hopping, skipping, sliding, etc. At one point, I worked with 5-6 year olds with special needs and this was their favorite part of PE.
Hope this helps! I'd love to hear how this progresses.