Well firstly, unless you’re using a custom cursor - you’ll get a rollover cursor - I use a sight and gun that follows the mouse - (you can download a fla on this from my site).
Also, making multiple enemies and making them mcs into buttons gets fiddly - you have more flexibility with actionscript for an mc, than with a button.
Anyway - it’s your game, but unless there’s a reason for it, don’t use the enemies as buttons because is much easier to do the hit animations as mcs - if you looked at the tweenies game you’ll notice that only if you hit one of them on the actual mc surface area, a hit will be registered, and the hit animation is played. This is much smoother and easier than sticking the mc in a button.
The code I posted can also be used to treat an mc like a button - an easy way to get rid of the roll over cursor.
But like I said before - it’s your game so use whatever you want.
Although Kirupa forum is an excellent resource for general flash tips (esp. for newbies), if you want advice on gaming only - check out the games forum at flashkit.