I considered joining a gym but let the idea go because like other members have said: walking is more interesting and cheaper and I don't have the support network to arrange childcare... plus i like to actually exercise with my kids.

I walk 3km every school day x 2 so that's 6km per day (it's 1.5 km one way) ... my 5yo flies ahead on his scooter... I push a pram... it's hilly and I get my heart pumping up to 180bpm. I figure I'm not only saving a fortune in gym fees i am also saving on petrol and wear and tear on the car! This will stay as my main source of exercise for a few years to come. When I don't need to do the school run I may consider joining a gym for the discipline of it.