Gary, bringing in sand will not help, and really, neither will concrete; The water will still be there, it's just covered up. Covering it up may help reduce mildew smells and moisture problems that could occur in framing, but it will not do your foundation any good. Quite simply, that water has got to go somewhere.
It's very common for the dirt level in a crawl to be 18" to 36" lower than the yard, and raising the soil level in the crawl may also be impractical because of a lack of room to work after filling it in.
I think a sump is going to be your best bet here, but if you would answer a question or two first, we'll see just what else you may be able to do.
First, I'm gathering your lot is very flat overall; is there any drainage slope away from the house, say within the first 10'?
Also, what is the exterior finish of the home? If it's brick, how far is it from the ground level outside to the bottom of your crawlspace vents? If it's siding, how far from the ground to the bottom of your siding?