Use whole/cracked/sliced/chopped spices. Powdered spices will continue to add spice flavor until it has all been extracted, which will likely be too strong. Once powdered spices have been added, you cannot remove them without filtration; they also tend to make a mess.
Use a hop sack to contain the spices, you can weigh it down with a couple of sanitized, lead free glass marbles if you like. If you tie a piece of fishing line to the hop sack, you can use the bung to keep it in place, making it really easy to remove the spices once your desired flavor profile has been reached.
I'd be sure to add yeast nutrient/energizer & DAP for a healthy fermentation. Also, I'd roughly chop those raisins in a food processor so the yeast can get at all that raisiny goodness; same with the dates. A dose of pectic enzyme at the beginning of fermentation will do wonders to help break down the fruit & will help to clear your cyser. I'd also give it a dose of sulfite before pitching yeast, but wait to add pectic enzyme till at least 12 hrs after sulfiting & be sure to aerate well before pitching yeast.
Your recipe sounds very much like Ken Schramm's Falls Bounty Cyser recipe; I've made that one & can tell you it's VERY TASTY! It's going to take a year or two for it to age, but it's worth the wait. I think you're on your way to a tasty cyser!