That small of a fan shouldn't do any damage. I keep my seedlings and small clones below the full-force (lowest setting though) of the oscillating fan, but the fan remains on while lights are on. In flower I don't EVER turn the fans off unless it's to take a picture.

I have two grow rooms right now. An indoor "growth" room (400w HPS) and an outdoor flowering shed. (1000w HPS) As long as the seedlings aren't overheated and as long as the soil doesn't dry too quickly, they should be fine under your 250 MH. Keep a close eye on 'em (no problemn there, I'm sure, lol) for the first couple days so you know what you're dealing with. If normal light distance is 9" from tops, raise it to about 18 inches and watch the seedlings' reaction. Slowly lower it over a week or so till you get the light to a "normal" distance. To determine "normal" distance...Stretch-out your hand, place it palm down, just above the tops of the plants, below the warmed-up light. If your hand can tollerate about a minute without getting pretty hot, your acclimated seedlings should do fine. (don't touch the bulb)

You can also do fine with CFL's, but I much prefer HID's for lumens and penetration.