Hi there
Could've written your post myself. 2 boys, exactly the same ages, love em to bits but getting them moving in the morning and coping with that mad hour around bed and bath has been a real trial just recently.
Like you say, most of the time they are lovely, its just the start and end of the day (when they are tired) that can be tricky.
Don't know about you, but we find the closer it gets to bed/bath, the crazier (and louder) the kids seem to get. It is usually the 6 year old that leads the mayhem, whilst the 4 year old has just got to the, "I have to do what I'm told at school, so I'll challenge everything I'm told to do at home instead" stage! (I remember his brother going through the same thing at about the same age!)
As avenap suggested its seems in our house to be best to tell rather than ask at these times. (They are far too wound up and tired to be reasoned with.) We have also developed a zero-tolerance to back-chatting and tempers and they now clearly understand that they are not to say no to us or argue/tantrum and if they do, they have to go and sit on the bottom step of the stairs (luckily for us we have a particularly small, boring hallway and they both hate having to sit there).
We have also started waking them up 20 minutes earlier in the morning but leave them in bed to give them time to shake off the grumps before coming downstairs and we have altered their bedtime routine slightly to allow for a bit of 'divide and conquer' as not only do they then both get a bit of all important one on one time with Mummy or Daddy, it also helps to calm the atmosphere.
Generally we tend to repeat the 'this too shall pass' mantra on a regular basis to each other. Sounds simple but its sooo true, there have been other stages where things have been tough, but we survived .
Its been a long school term, don't know about your boys, but ours are absolutely exhausted and really ready for their holidays.