LOL. I didn't realize I didn't put the species of finches the kids are interested in . . . My son would really like zebra finches as he fell in love with the meep meep sound they make. I've read that zebra finches can be more aggressive than some of the others and that's why I was asking about the possibility of a M/M pair.
Here's another big thumbs up

for asking questions.
Zebra finches can be real buggers. No doubt. But all forums--as I'm sure you've noticed on the goldfish forum, and even here on the finch forum, or any other forum--are problem-centric. There's absolutely nothing wrong with that and they serve a terrific purpose! But it sometimes makes it too easy to start thinking that everything will be a problematic, joyless, never-ending nightmare.
If your kids are digging the zebra finches, they are in good company. Many people think they are attractive birds, enjoy their meep-meeps (as your son has already noticed), and find their active natures engaging. They are generally hardy birds and relative to many other finches are quite easily cared for.
As far as their aggressive nature and preventing it by getting a M/M pair as opposed to a M/F pair....
I personally don't believe that a single M/F pair of zebra finches is any more or less likely to exhibit unwanted behavior than a M/M or F/F pair. And I'd wager that the great majority of zebra finch owners have a single M/F pair and don't have any real problems. In fact, zebra finches kept as single pairs often form very strong bonds. Aggression problems mostly start when you have anything more than two zebra finches in a cage. If you don't plan to have more than one pair of zebra finches, there is no reason to avoid a M/F pair on the basis of aggressive behavior only. There are always outliers and exceptions, but they exist in single sex cages as well.
Whether you want to participate in the joys and tribulations of nest building, egg laying, and chick rearing is a different question.
