One thing I'll mention about blueberries is that it will make your mead kinda greenish...(mead is basically yellow plus blue). With that said, I'd do the primary fermentation depending on how you like your mead.
For a dry mead I'd go with about 10-12 pounds of a mild honey for 5 gallons, for a semi-sweet, about 15-16 pounds and a sweet mead about 20 pounds.
After the primary, go into your secondary and rack on top of the fruit. I use the Oregon fruit purees in a can that various homebrew stores offer. They're handy, and you don't have to worry about micro-organisms off of fresh fruit, possibly causing a bad batch. If you're going to use fresh berries, just wash them good and then I'd freeze them. Freezing fruit breaks the cell structure down and allows for a better "mush" in the secondary for flavor.
Hope this helps. Make sure you pick the right yeast also ... if you like it sweet go with a sweet mead yeast or a sweet white wine yeast. If you like it dry, go with that variety of mead yeast. I wouldn't use champagne yeast though, unless ... well you like champagne.