Old Glory, first off, do you know that you NEED a scope? Iron sights actually have some advantages over scopes (lot more rifles have iron sights than scopes, they're more rugged, and you can use the front sight to estimate range, for example).
I scope some of my rifles because I have a hard time seeing small targets at over 200 yards - plain and simple my eyes aren't up to more than that. I'd recommend you try shooting with iron sights first, then scope it only if you need to. (and you would need to scope your center-fire rifle, too, as I don't think you'll be using the .22 at 200 yards or above!).
Oh, and if you find you MUST scope your rifle, I recommend the lowest power you can use - I have a 2.5-7 on my .22 and a 3-8 on my AR and I practice with them turned to the lowest setting when I'm practicing at 25 yards. At longer distances, I turn them up only as far as needed to make out the target. I make students at the shoots I run turn their scopes down to the lowest power, too.
Most Appleseed shoots have the first day done at 25 meters with reduced size targets - it's easier to change out targets when you're not having to walk 400 yards! However, on the second day they do shoot known distance out to 600 yards depending on what the host range has available.