Pool filter sand is a nice substrate. I actually didn't wash mine at all when I added it to my tank, but I'd still recommend rinsing it a little. PLAY sand on the other hand you can wash for hours and it will still probably cloud your water.
-For some easy low-light plants, I would stick with the 40w fixture if you can get it working. I did a pretty densely planted low-light 20 gallon with a 20w fixture. The plants did great.
-As far as the driftwood and plants for the cycle-the driftwood will be fine during the cycle. Sensitive plants might not take the cycle very well, so you might want to hold off on the plants until after the cycle.
-It would be a good idea to wait 2-3 weeks after you get your new tetras (and whatever other fish you get, you might as well just get them all at once and just quarantine them together) to introduce your current fish.
-For stocking, since you already plan on 8 red-eyes, I would just add a little group of bottom dwellers and then maybe a couple centerpiece fish. I really like cories as bottom dwellers and you could have about 6 of them in the tank. For some centerpiece fish, you could do a couple dwarf cichlids like rams or apistos or a pair of smaller gouramis (I really like pearls, they get around 4" and are pretty peaceful)
That all sounds good. Thanks.
For the stocking, those are great suggestions. Cories seem to be winning for the bottom dweller group.