Hello Yummy Mummy,
You should have a look at different running clubs around near where you are based, I am sure there are people in exactly the same position as you - ie. cant not run in the morning or evening because of family commitments.
Where are you based?
If not do try what Nellie suggested - pop on the mp3 or ipod and listen to your favorite music! Good luck.
Real People, Real Fitness, Real Runners.
www.realrunners.co.uk