That's a hard thing- lowering the ABV while keeping the basic recipe the same. I've been working on several IIPA and IPA recipes, and without the high OG it just isn't the same. It's close, though, and worth doing, just so I can drink more than 1 in an evening!
The thing to do is keep the recipe basically the same, and just adjust all the grains and the IBUs down so they still scale.
You may find, though, that you need to add more character malt in some cases. What happened to me is when I reduced the OG by a lot, the beer lost much of the body and mouthfeel that I loved. So I added Munich malt instead of some of the usual base malt, to try to bring that back, and added some melanoidin malt. It's not a perfect fix, but it really turned out well.
In order to do the exact fix that will work, you'll probably have to brew it with a lower OG by scaling all the ingredients and then tweaking the fixes with the next batch, if that makes sense.