Honoring God, Honoring parents

So it says in the bible that we must "honor your father and your mother", which most of the time is easily done; clean your room, don't break your curfew, be nice to your sister. But what about when it goes against what God is calling you to?
About last fall I was asked to start leading a hub group(a.k.a. a cell group). Well, I thought, it's a little nerve wrecking, it's a lot of pressure to lead others, but hey, if it'll help in building God's kingdom, why not? I want to serve. So having Christian parents, I asked, thinking I already knew the answer, but I was wrong! The answer was something like, "You're busy, it's your grade 12 year, you're working, you have other commitments". Alright then, next year it is! Come this fall, I've graduated and I asked again. Same answer! But first year of university, not last year of high school.
I just don't understand! It's only an hour a week, I don't need to prepare for hours on end because I can get it straight out of church, youth group, and my devotions. So what's the big deal? I don't start until school until January, giving me time to get used to leading. I would grow so much if I were to lead a hub group. It keeps you accountable to how you live your life. If God wants me to lead, he'll make things work out. If not, he'll close doors. Easy as that! I want to honor my parents but I know that I have to honor God above them. Since when was it so wrong to want to grow in your relationship with God and serve in His kingdom?!