Sure, you can start fermentation without it, a lot of apple wine recipes call for acid blend due to the juice having less acid than desired in the end product. I'd say go for it as is, you can always add acid blend later if you feel the wine needs it. If you do decide to add it later, be sure to mix it with a little (about 1/2 cup) boiled & cooled water. Adding dry powders/granular things to active fermentations can cause the dissolved CO2 to suddenly come out of solution, resulting in a foamy volcano-like eruption from your carbouy.
Regards, GF.