First off, welcome to the forums.
Secondly, this should probably have a "Spoilers" tag in the title so people know to not read it if they don't want to run into possible spoilers. (My post will contain small spoilers, by the way.
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Now, to answer your question. I'm not sure, but it sounds like you are fairly low level to try that quest. I'm sure you
could do it, but I advise you to take on some of the starter quests first. That's what I did, at least. Go to Megaton, help Moira out with her guide for experience and items, fix the valves for the water purification guy, disarm/blow up the bomb, and the like.
In particular Moira's "Get food/medicine" quest (or whatever the actual name is) is a great starting quest that will net you some nice equipment. You run into some raiders at the super market, and they'll drop some guns and armor that will give you a nice boost in the early game. You can find Hunting Rifles and Assault Rifles, among other things. (EDIT: Oh, definitely complete the bonus objective, find the medicine, before talking to Moira and completing the quest. There's a whole room full of junk toward the back that I actually missed the first time.) Great way to start the game.
As to the ants themselves, if you really want to finish that quest now, you can try picking them off one at a time, from a distance, while sneaking. That's what I did, although it will probably be difficult for you as you only have a pistol. How I did that level was sneaking around with a Hunting Rifle and, from Sneak, while hidden, sniping the ants' heads, which usually results in instant kills.
In conclusion, my advise is to go back to Megaton and do some other quests, then come back for the ants at a later time. Good luck, have fun!