How can I fit in more cario?

Hi,

I am new on here today so bear with me, please.

I decided to increase fitness and lose weight just under a month ago and so far have lost about 12lbs and a few inches.
Judging from the guides on here I need to increase my cardio. Currently I do the 'park' workout of ibodz, which is 2 x jogging (I do it on the spot, knees up etc), squat thrusts, press ups, double crunches, dynamic lunges and I have thrown in some hand weight work for my arms. This takes an average of 40 mins all together and I watch my favorite programme on dvd (only time I watch any telly so keeps me motivated to do it)

I am a stay at home mum of a 5 year old and 2 year old twins. At the moment I exercise while the twins are asleep during the day or after the eldest has gone to bed at night. I can't leave the house at these times so am stuck to indoor activities. I can't afford any equipment.

Has anyone got any ideas what I could do to increase my cardio that won't take too much more time? By the time I have worked out, showered and done housework there is no time left! I walk everywhere as I don't drive so activity levels during the day are moderate.

Thank you!