Two hours of homework is excessive for children that young. I feel that homework should not take over home life. The guidelines for homework state that it should be about 10 minutes per grade so a first grader should have 10 minutes per night and a third grader should have about 30 minutes. Anything above this is excessive, in my opinion.
I would speak to the teachers and tell them how much time your kids are spending on their homework. Either they are giving too much homework, or they're not explaining the concepts and your kids are struggling to understand how to do it, or there are learning issues that need to be addressed.
If the teacher is unwilling to address the problem I would then go to the principal. In my opinion it is unacceptable for children in elementary school to be unable to participate in extracirricular activities because they have too much homework. Not to mention it interferes with family time, which is important.
To regulate homework my son was given a timer and he was required to do the appropriate amount of homework each night (30 min third grade, 40 min fourth grade, etc.). Once the time went off he was finished for the night. If he got up to get a snack or go to the bathroom, he turned the timer off and started it again once he returned.
I've heard from lots of parents in your situation and the only way to change it is to insist on taking back our children's lives by limiting time spent on homework. This can be done by banding together as parents and speaking to the school administration and/or the school board if needed. I feel that as parents we should take back family time by insisting that our children spend no more than the recommended time on homework. I insist that my son only do the recommended amount, unless there's an extenuating circumstance. I feel it's within my right as a parent to regulate and monitor his time at home rather than have the school dictate what he does with his free time. The school is in charge of school time and I'm in charge of his home time.
Good luck!