Don't worry too much about turbid mashing -- I guess you won't have a particularly traditional lambic without it, but you'll get a very good beer.
I've made a few beers, both traditional lambics and sour beers with not so traditional grain bills using nothing but the Wyeast lambic blend. You can ferment just fine with that alone as it includes some un-named strain of sacchormyces in addition to the bret, lactobaccilus and pediococcus. I have 12 beers left from my original attempt back in late 2008 that has really come into its own now. That said, my wife (who I brewed this for originally) and I both like very sour (Cantillon Geueze) beers, and this is only now starting to pick up that nice acidic tang. Before that it had some acidity, but predominantly horsey, barn yard type funk from the Bret. Raspberries will add some additional acidity, as well as some wild yeasts of their own if you're not careful.
If I were you, I'd just pitch the Lambic blend and let it ride for at least a month in primary. Then put your fruit in secondary and rack onto it. Someone on here will know how to make sure the fruit is sanitized enough that you don't have to worry about local wild yeasts "infecting" your lambic. Since the bugs will eat most of the raspberries, I don't think you have to worry too much about pulling it off the fruit. Someone else who has more experience with this may have a different opinion, though. Then let it sit in secondary for a god 6 months while the wild yeasts chew through the dextrans and starch from the wheat and raspberries. Once you bottle it, give it another few months before digging in.
Good Luck!