In reply to islandlynx:
In my experience of doing VF, the end of august would be fine as there were plenty of climbers about then (and the end of July) but bear in mind you could be looking at 20+ degrees on a south face on a nice day in shorts and t-shirt to 5 degrees on a north face on a bad day in all the clothes you can muster, fresh snow above 2500m anytime due to 'freak' storms and/or rain for the whole time you're there. You've got to be prepared for everything because....mountains. Perhaps a better way of thinking is 'what other things are important?' e.g.
1)space in huts and accomodation prices in general - august is peak Euro factory shutdown month and everyone and their dog goes on holiday. We've never had trouble getting the small rooms in huts during the week when booking a day or two in advance, but never tried weekends as we avoided them. At other times of year and in other places Friday nights at 'edge' huts (ones with easy access close to civilisation) get busy with people going straight up after work intending to get a full day's walking/climbing in on saturday. I would expect the Dollies to be the same.
2) bad weather options - Arco is much lower altitude and warmer - like 10+ degrees warmer. It's 2 hours from the Brenta dolomites. Too hot in August really unless the weather is cold, but your best bet for getting something done in a week of Dolomite rain. the problem is that it's way more touristy and could be difficult accomodation-wise if you're not pre-booked anywhere.