So what's a fairly normal level of complaining about homework, or work in general?

My 1st grader is such a grouch this year. I'm trying to support him and figure out if something is off. He has about an hour of school homework a week and another hour of math homework for AoPS outside of school. But he keeps complaining that he has homework "ALLLL the time" and so much more homework than his 3 year old sister. (Hmm, yes?)

I'm disappointed in his crappy attitude. I told him he could quit AoPS if he wanted (he does afterschool math because he wants to after all) and then he balked and said he wanted to stay in that but didn't want to do the homework on the weekend. So now we'll try to get his AoPS and school homework done by Friday I guess. He has a moderate level of activities -- he's busy but not ridiculously so...

Is he just being a 1st grader? Or should we keep tweaking this until we find something that works better?

He has all these opportunities... great. But if he's just a sulky unhappy kid, I feel like we're missing the point.