I'm sure Martin will chime in eventually, but basically what I've learned from him and many others on this forum is for Hefes/German beers in general, using soft water is better. Calcium to 40-50ppm keep sulfate/chloride to 20 or less ppm. Use lactic acid to correct for mash pH unless you are using undermodified grain and doing a Ferulic Acid rest. If so, no acid addition until you check the pH during beta rest.
Edit:. To be clear, whether or not you are using well modified/undermodified grain, if you do a Ferulic acid rest, wait until after that rest and 10 mins into your sacc rest to take a pH reading and then, if necessary, adjust your mash pH to 5.4 (ideal) using lactic acid. You're safe in 5.2-5.6. just try to get in that range if you have the means to take a quick pH reading with a temperature adjustment.
A note on the grain modification: I said that because I confused acid rest with protein rest and you should do a protein rest if using undermodified grain, however most grain us homebrewers get is well modified these days and there's often no need to do a protein rest and can actually harm the head by doing one with well modified grain.
Apologies for the confusion, just wanted to clear that up. I may be incoreect, but this is basically what I've learned from others here. A lot will depend on how you're doing your mash, by the looks of the recipe, I'm guessing your doing a straight single infusion. I say that because if you were to do a Decoction I would skip the melanoiden malt as you will get some color from the decoctions.
Good luck, don't over think it, if you are in doubt, err on the side of softer water and just focus your efforts on getting the correct mash pH.