I have some sympathy for the OP, here. I have 3 dc- 2 at school, 1 pre-schooler, and 2 dogs. I work p/t (1.5/2 days a week)
The dog-walking, for an hour, often in foul weather, I don't see as a "leisure activity" at all! I love my dogs, but the need to walk them is often a pain in the butt. Those of you who have suggested the OP walk the dogs and the kids to school have never met my dogs. They need to run, so I need to take them to a country park- a sedate stroll on the lead round the pavements wouldn't do it for them at all! Plus the anxiety that they will poo on the pavement and it might be runny- yuk!
I too fill every spare hour with a "chore". I think it might be because I always worked f/t and long hours before I had the dc, since I have become a SAHM (p/t) I feel I need to do the job as if it was a paid role- I even have a housework rota, and get unsettled if something comes up that means a certain room doesn't get done at its allotted time 
I realise how sad that sounds.
I agree that washing/ sorting/ drying (5 airers for me)/ putting away/ ironing/ putting away takes more than 5 minutes. I think I'm fairly efficient at it (I'm not a dilly-dallier), but it still seems to take a fair bit of time, and on a washing day (3 loads, twice a week, and towels and bed sheets at the weekend) I can be still hanging up washing at 11pm.
HOWEVER, this thread has brought me hope! I'm about to go back to f/t work (own business) and was worrying how the hell I was going to maintain standards here as well as working out of the house 8.30-6.00, but seeing this has made me realise that I am guilty (as possibly is the OP?) of making my SAHM jobs into more of a JOB- possibly through guilt? I do feel too guilty to sit and watch TV/ read a book during the day, and maybe, just maybe, I have arranged lots of tasks to make me feel busier (and therefore more justified?) than I need to be, so thanks all!
Have also gained faith through this thread that I WILL manage the transition to f/t work without the house falling down around my ears! 