We also have a family member who will be our MC. His job will be pretty simple...like you said--just introducing people before speaches, making announcements, and making sure things flow well, etc. And our reception is very short, so it's not a long gig. And we're pretty much giving him a script for the whole thing, so he won't need to do much preparation on his own...
Maybe you could ask someone to do this as well? I think you would probably feel more comfortable having someone you know do it, as opposed to an MC supplied as part of the package...