My mum is a disabled teacher, she has reduced mobility obviously and she has no problems. She generally teachers ks2 but has taught ks1 if necessary and teaches ks1 1 day a week at the moment.
No one bags an eyelid when my mum can't sit on the floor with the reception children and has to sit on a chair.
She can teach pe, again no one bats an eyelid that she can't demonstrate everything fully. She can demonstrate hand movements for things like throwing, tennis, netball etc the only thing she can't do is run around or gym, but lots of teachers can't do that anyway. If she needs to she can get a child to demonstrate.
On the very rare occasions that a child has run off in her 20yr career in primary someone else has had to chase them, normally there is a TA at least next door. Again no one bats an eyelid that someone else will have to do this worst case scenario.
She can't restrain a child but she is very good at calming down angry children, she is good at discipline and I don't think she's ever had a situation where a child would need restraining under her watch (It has under other teachers at her school though)
She is a good, well respected teacher (i know this because i was taught by her) her disability impacts her ability to teach precisely 0. We can easily make allowances for disabled teachers to enable them to do their job so why can't we make allowances for someone with reduced mobility for other reasons?
When we teach heath to primary children we shouldn't be teaching them about weight, we should be teaching purely health. Most young children shouldn't have made the connection yet between overweight and unhealthy, I doubt that ks1 children will find it hard to learn about health from an overweight person 
Also I knew every teacher who smoked when I was at primary and secondary, I was still able to learn about anti-smoking and healthy eating etc. From these teachers. Funnily enough my nutrition lecturer at university was v. Overweight. I was still able to learn about nutrition from her because I recognise that theoretical knowledge isn't always put into practice and there are a multitude of reasons why someone might be overweight.