Mr. Malty and Yeast Calc are good tools. I would skip entering the manufacture date. They estimate viability very low compared to cell counts I have done. Also, for yeast propagation, a single step of 4L might be a little large. (It will take longer to generate the cells and use more DME per cell produced) If you want to get the most yeast for your DME then the inoculation rate should be about 65 million cells per ml.
If it were me, I would step it up dailiy based on cell counts, but if I didn't have a microscope I would do the following:
1) 1.5 liters with 150g of DME in a 5 liter container or larger. Culture for one day on a stir plate.
2) add 1.5 liters of water and 300g of DME. Culture for one day on a stir plate.
3) add 1 liter of water and 400g of DME. Culture for two days on a stir plate. Crash, measure slurry in ml. Estimate 1 billion cells per ml.