Wow. It does sound as though you have your hands full.
Putting your elder son to bed a bit earlier might really help to take the pressure off you as it would lengthen your evening significantly.
Neither of my children take daily naps anymore. They both quit at the age of 2.
I put them both in bed at 7:00. (Though that was easier in the winter!)
That gives me a little breathing space and time to myself in the evening.
Weaning your son off his naps shouldn't be hard. Just organise playdates, trips to the park etc for a few days to keep him busy and prevent him having the chance to nap. He'll be tired and you should notice an immediate change in him wanting to go to bed earlier.
Personally, I do my laundry first thing in the morning. I put the wash on as soon as I get out bed, before dressing myself and the children. By the time we have finished breakfast it is ready to hang out. Folding up the previous day's clean laundry and hanging out the wet load is all done before I leave the house on the school run. It dries during the day and is ready to be taken down and folded the next morning.
I do one big supermarket shop a week. I try to do it every Friday so that I have a full fridge to start the weekend. I occassionally go on Thursday.
I go first thing in the morning, after dropping DD at school. DS only goes 3 mornings, not including Fridays, so he usually comes with me to destroy everything in my trolley help.
I used to clean my house in once or twice a week splurges of a couple of hours. These days though, I find I can't concentrate on it for so long without being distracted. Instead I have changed to cleaning one or two things each day. I hoover the house every two days or so, clean the bathroom once a week, clean the kitchen when it needs it etc. Most of my cleaning gets done in the morning, leaving afternoons more free for the children.
I definitely agree with you about getting the children to help. I have recently made more an effort about this myself too. I now try to get the children to bring their bowls/plates/cups to the kitchen after meals. I also get them to clean up toys after they've finished playing with them and put books away. I struggle with my DD who changes her outfits up to 10 times a day leaving a trail of discarded clothes in her wake.
My DH tells me off for trying to tidy the house as we go along throughout the day. He says I should leave it like a pigsty until they go to bed and then blitz it. I know he's right and it would be easier, but I don't like living in a pigsty and I stubbornly try to clean things up as we go along.
Do you try to spend all your time with your children?
Personally, I do read to them/play with them/help them/spend time with them etc, but I am also prepared to say 'no' to some of their endless requests for my time/help/attention. Obviously they are important, but I want them to realise that they are not the only focus in my life and that I have other things that sometimes need to be dealt with. I am quite happy to say 'sorry, I'll help you in 5 minutes, I have to go and clean the bathroom first' etc. I honestly think it does them good to have to entertain themselves, work out a problem for themselves etc rather than expecting mummy to jump to attention everytime she's called.
I wonder if any of these ideas would be useful for you? :)