Starting with soft water and relatively lower amounts of all the important ions, you're sitting in pretty good shape in that you can add pretty much whichever salts you want to match whichever water profile you want (or at least with little dilution).
The MOST IMPORTANT part is getting the mash pH down around 5.2-5.4. Adding enough lactic acid to achieve that might give your brew a sour taste, though, since you're starting around 9 with your base water. So, like squiggy said, you can bring it down with CaCl2 or gypsum, if you don't mind the ion contents changing.
I use this often (in conjuction with brewater 3.0):