Sand adds the virtue of drainage to otherwise dense soil. If you have good loamy soil, you really don't need to add any. If you have heavy soil, or are planting in pots, it is a good idea to add about 1/3 of the mixture as horticultural sand.

You can plant as long as your ground is not frozen, and I would get in there real soon if I were you.

I'm just down the road in Newport News. No sand necessary around here for any of those bulbs, and you can continue planting right on through New Year's (the ground never freezes permanently in this zone, only for a day or two at a time, usually). I would recommend mixing in some sharp gravel when planting tulips and crocus; "permatill" or "soil perfector" are name brands available. This is not so much needed for drainage as to keep voles from eating your bulbs as soon as they're planted. Daffodils are immune to attack, being members of the amaryllis tribe, but the lily and iris families (to which tulips and crocus, respectively, belong) are prime targets. You should also be aware that, although the daffs and crocus are pretty much perennial, most tulips are good for a season or two at most around here. Our summer temps and erratic soil moisture aren't conducive to their becoming naturalized. Although some classes tend to last at least a little longer than others, it's probably best to consider tulips annuals, then to be pleasantly surprised if you do get a bloom or two the following year.