Jellylove, yoga might suit you.
Go to a class, maybe lunchtime near where you work, and then do a little bit of practice every day at home on your own mat.
I've found running terrible for my hips (old injury from ballet) and yoga is something I can tailor to suit myself. Some days I feel like doing restorative poses, and gentle twists, and somedays I feel like doing more standing warrior poses, or inversions.
If your DCs wake up, you can go into them (if they want only you) and then get back to your mat, which is why I love it (bad sleepers).
Regarding diet, the most effective thing I've found if a low GL diet from Patrick Holford. I didn't even notice that I was eating differently, just felt energised and alert, and the weight melts off.
It is difficult to find the time for yourself, but you owe it to yourself to enjoy your body, and your life, and being fit and healthy is very good for your kids- they learn from you whether you're teaching them or not!!