bigmac you do know you just described a civil union right? Those have been around for a while now. The problem is that by having to place a special label on same sex marriage to "uphold tradition" you're still just saying that the two types of marriage aren't equal.
Then you bring family into it which, nowadays at least, have little to do with marriage. You can have children without being married and vice versa. Also there's this thing called adoption that some people like to try when, for whatever reason, they can't have children naturally. I seriously hope you're not saying gay people shouldn't get married because they can't have children naturally.
The problem with traditions is that people sometimes just blindly follow them. What practical function does having only traditional marriage serve society today that will disappear now that same sex marriage is legal?