DH & I had another big discussion about when we're going to tell last night after I posted, and we decided that we're going to wait until my parents get back from their vacation in mid February to tell everyone that we're expecting. I realized that all of my reasons for wanting to tell them now were more trivial than his reasons for wanting to wait. Because we are so close with our families (they all live within 10 minutes of us, and are at our house all the time), DH feels like he really wants this pregnancy to be about us as much as possible. Not that our parents are dramatic, but this will be the first grandchild on both sides (and the first great-grandchild for three out of four sets of grandparents) and as soon as we tell, it will cease to be about just us anymore.
DH is really funny about this being "our" pregnancy and "our" baby. I don't know if it's because he doesn't feel like he has much control over the pregnancy, but he can control who knows. I almost feel like I'm cheating my parents out of this time that I'm pregnant, but I know that how DH feels about this is more important. All the reasons that I have for wanting to tell now (wanting to see their expressions, general impatience, etc.) seem a little trivial when he acts all sweet about wanting to enjoy this time where we're the only ones that know.
Re: We're waiting to tell
I can completely understand this. We had virtually no time where it was just "our" new family... no time to even really get used to the idea ourselves before the entire world was involved. Everyone was (and is) super excited for us and sharing the news was really, really fun, but if I had to do it over again, I'd definitely wait until after our first doctor's appointment to tell. Look at it this way, after telling them they'll have that much less time to wait before baby's arrival!
Good luck with keeping it a secret til then! Especially if you see the families frequently... even in the short week we waited to tell everyone, I caught myself several times almost spilling the beans.