I went the cheap and easy route. I bought a brewer's best weisbier kit (2 cans of wheat LME, no steeping grains & French Strisselspalt Pellet Hops** (smelled like a piney noble hops).
I figured that since this was an experimental beer for me, I didn't need to invest in a pricey build your own set of ingredients from the LHBS. The LHBS wanted about 10 bucks more for the OP recipe.
I pitched it on an entire cake of WLP 011 German Ale yeast late Saturday night (the 6th). I had just moved a kolsch to secondary so the yeast cake was 'exposed' for less than a minute. Airlock bubbler activity started within a few hours. With such strong bubbling, I expect to have it in secondary on Sunday (7 days primary) with watermelon juice. I'll let you know how it turns out.
As a side note, this kit with the 'german' dry yeast from Brewer's Best was great with some blackberry extract a few months ago. I expect nothing less for this kit with watermelon juice added.
** - From Midwest web site: "2.6% Alpha Acid Content. Considered a good aroma hop with medium intensity and pleasant hoppiness similar to Hersbrucker, and often preferred to it. Used for Pilsners, Lagers, and Wheat beers. Substitutes: Hersbrucker, Mt. Hood, Crystal."