Jenn,
I would love to keep in touch - my husband and I are 27 and 25 respectively and we just adopted our little boy 4 1/2 months ago. So, I know what you are talking about! also, we both look pretty young too, so we get that a lot as well.
With the agency we went through, there was no age requirement, only a marriage requirement of being married atleast 2 years...which we had done, so it was so problem at all. Yes, we also saw that we were too young for China, which was fine with us, but that seemed to be about the only place that could have been a problem. Hopefully you will find the same. I would love to hear more as you progress, since we sound somewhat similar! Please don't hesitate to PM me or ask anything - and either way, keep us posted on your adoption process! Best of luck and God bless you as you start this adventure!