Around here, we typically advise newcomers to dose all chemical separately just because the math can get tricky. If you can handle the math and keep good notes, the other sources of chlorine are fine to use. Just pay attention.
Since you know the total CYA you want to add, you can calculate the volume of dichlor that equals(see Pool Calculator, Effects of Adding Chemicals, at the bottom). Then use that dichlor over a period of days to raise FC. When you have used that volume of dichlor, switch to bleach or liquid chlorine. You should recalculate all your values, probably daily, to be sure that as CYA increases each day, that you are aware of the changing values for min, goal, and max FC (max being mustard shock FC for that CYA). It is a bit of a challenge and only the truly nerdy ought to follow that path, IMO. (Today dichlor raised CYA to 25, so new FC goals are blah, blah, blah, tomorrow CYA will be....)
It is way easier to just put in the CYA you need and be done with it, it is there, you know it is, and you know that eventually it will show up on test, this week or next. Then you can focus on FC, or pH and then FC as the case may be.
That dichor will keep just fine, you will have a chance to use it eventually. Probably next spring, when CYA is just a little low.