I think that might be a little low. Others can chime in, and my Belgians haven't been that big, but I think 68 should be fine to start with most of the Belgian yeasts. How high you get it depends on the yeast, and you normally raise little by little after a couple of days.
I used WLP500 for the last Dubbel I made , it was cool outside, the garage refrigerator got cooler than I liked a few times, and my wife was in the hospital with cancer complications that were terminal, so I called it Out of Control.
The beer turned out wonderful and helped me through some very trying times at that alcohol level, and it was nice to sip on one here and there.
Bottom line, get a good yeast made for that style, read what the yeast likes. start normal, ramp up little be little.
You will want to mash low, maybe 148ish. You probably want to dry it out with some sugar, maybe quite a bit if a Tripel.
Looking at your other post, make sure you pitch healthy. High alcohol beers need more yeast.
