I recommend that you follow the instructions. This non-saccyeast (40% of your combo) is VERY sensitive to non-chloronated water temp. You want to keep it between 68-77 degrees F. I've seen the charts on how badly the yeast does if not in this range. Rehydrate the yeast without stirring - pour the yeast on to the water and leave undisturbed for 10 minutes (you can clear any clumps or mounds so that most of the yeast is exposed to the surface of the water. After 10 minutes add in some of your must and stir. Try to get the temp of your starter and the must close. Wait 20 minutes and then apply throughout your must. Go Ferm is not recommended.
I'm using the non-sacc yeast, Prelude, this year. Similar instructions.
Good luck! Please report back on your results with Melody.