There is no such thing as a dumb question! ;)
I have longed my horses over poles quite a bit. I don't have a problem with them trying to avoid the poles if I am concentrating on keeping the horse tracking in the correct line. My horse knows he's suppose to stay at the end of the longe line. I have taught him the aid "scoot" by pointing the whip at his belly, maybe flicking it so he scooted back over. If he starts drifting in, I just remind him this way and he goes back to the intended path.
If you're really concerned about him trying to dodge the poles, you could put two or more poles together into a really looong pole, so there is absolutely no way he could just simply walk around it. Be prepared to have to push him a bit to get him over the pole the first time. After he realizes he's going over that pole no matter what, you should be able to take away the extra poles and just use one. The most important thing in your job as the trainer is to make sure he stays on the correct path, so once he reaches the pole he will be in the center of it.
I would start him off on one pole and get him used to stepping over that before you add more. I have longed horses over poles before with four poles, each one placed about a quarter way around the circle. Doing this after longeing him over just the one pole might be an idea before you start adding a series of poles. (see diagram below)
As far as spacing a few poles that are right next to each other, start with about 18" to 2' apart for a walk, but it's not really a set distance. If you notice your horse having to adjust his stride much, or knocking the poles, then that's a sign they need some adjustment. If you ask him to step over many poles close together, you'll have to adjust the poles so they follow the arc of the circle - not just laid out in a straight line (see my little diagram below =D). This won't be a big problem if you are on a 60' circle, however.
Hope this helps!