I work from home at my computer and have two small children, my nearest gym is far enough away that a 60 min workout means being out of the house for 1h45m.

If I take the baby and the preschooler for a walk the furthest we can reasonably go before he's tired is 5K in around 65 minutes.

I have at my disposal a farm yard, some fields, old car tyres, tractor tyres and general bits of wood.

Any suggestions for how I can fit in some good regular exercise around work and childcare?