I am for the sake of the argument assuming this is not an Aprils Fool.
You have three small children you say, and YOU go out running early, so, that means your wife cant have morning exercise? Is she still in bed, or sorting the kids out while you are out looking after yourself?
I want to exercise. I have wanted to exercise for the last 12 years, since our oldest was born. My dh has been very kind and considerate, every evening he will tell me "first dibs to go to the gym". I say "you go" and I know he is disappointed that I dont go.
But you know what? 8pm is way too late for me. Getting up with the kids in the morning, work part time from home (and do an MBA), do the school run again for 3 pm, cook tea/dinner, take kids to activities, clean up after dinner, sort the laundry, ensure homework is done, and help with homework, by 8 pm I am too tired to go and do exercise.
It took me until now to find something that works for me and that I enjoy. I now do two exercise sessions per week outdoors intervall training in the park with a group of people (similar to British Military Fitness) after I drop off to school in the morning. Zumba 6 pm once a week, so three sessions a week.
You cant expect her to do as you want when you think she should, you need to facilitate that she gets to do what SHE wants, when she wants it.
We also go for hikes and cycle rides as a family on the weekend.
After three weeks of this I have lost some weight, my butt and my tummy are firmer, and I feel much better and much happier.