I'm frightened this is going to sound like boasting, but I do wonder exacty what you are doing with your time all day if you have that much time to spand on cleaning/cooking/shopping/washing every single day.
I'm a sahm with 3 kids in school, age 7, 9, 11. The reason I don't have a paid job outside the home is due to mental health problems which mean I have appointments twice a week which are very tiring, but I still do all that the OP does (apart from the dog - eww could not stand having one of those).
I also volunteer 2 (full) days a week as a literacy tutor for young mums who left school with no qualifications, get my children to activities (football, beavers and piano on Mon, Violin on Tues, Accordion and cubs on wed, Spanish class and Guides on Thurs, swimming on Friday) all on public transport or walking as I can't drive (medically). My dh works a 60 hour week minimum with 2 overnights away.
I do all our admin, financial stuff etc as dh just doesn't have time. I also have to do all the stuff you talk about in the evenings, homework/reading etc, and I do it all in a language I am still learning as my children are in a bilingual school.
I think it was rude of your Uncle to question what you do, and if you are happy, then great. I am sure that there are people on here who think I am wasting all the time I have while my kids are in school. But the things you describe like checking emails and ironing and decorating - those are the things I do in my spare time after the kids are in bed/at the weekend etc, and I'm a sahm! I do notice you say your ids are rarely in bed before 9.30 which probably also eats up a lot of your time, mine are in bed at 7.30 (little one, 7), 8 (middle one, 9) and 8.30 (biggest one, 11) with half an hour reading time once they are in bed.