One of my favorite beers of all time! What took you so long to come around to the "dark" side?
At any rate, I advise you to check out Brewing With Wheat
by Stan Heironymous if you are interested in attempting a clone of this beer!. Not to mention it is a great read. I believe he covers Adventinus in Part III and gives a basic rundown of the recipe. I don't have the book directly in from of me, but if memory serves the recipe is 50/50 to 60/40 wheat:pilsner with a small percentage of chocolate malt. I believe the decoction schedule is in there as well. If you plan on brewing this beer with multiple decoctions I don't believe you will need all of the dark malts or crystal malts as the decoction will create those complex melanoidin reactions and flavors. I also think the WLP380 Hefe IV is a more appropriate strain for the Adventinus as it has more clove characteristics, which is what you want.