Don't skimp on the reinforcement if you want to minimize shrinkage cracks. Consider going from 2' pattern to 1' (or even 18"). (not a cheap option either) Plan the control joints to be where you WANT the cracks to be. (under walls) Consider fiber reinforcing if you will have a floor covering. If you need the workability, plastizer is a great help, although not a cheap addition, but better than the cost of additional powder, which doesn't help the shrinkage problem anyways, as pointed out. Proper curing is essential.
Concrete is not cheap, and it's more expensive to do the second time. The foundation is the start of the build process and it's intended to outlast the rest of the building, spend your money wisely there, save money on the shingles, they are much easier to do-over in 10 years.