Take it from someone who has been collecting Slingerland exclusively for the last 15 years, as much as I'd love to see Slingerlands bring in that kind of price, it just isn't realistic at all. They always bring less money than the other big 3. Which is a shame, because the quality of sound and build is just as good or better in some cases. But hey, thats why I collect them, a top notch instrument at an affordable price.
$3000 is a very high estimate in my opinion. There are collectors grade Radio Kings from the 30s and 40s that sit unsold at those prices. You might be able to pull in $2000 as a complete set, on a good day. I think in a no reserve auction on ebay you'd be looking at around $1000-$1800 for the drums, probably closer towards the lower end. I would sell the cymbals separately. If the cymbals are all indeed A zildjians, you may be looking at another 400-800, towards the higher end of that if they are trans stamps in thin weights. Shoot some pictures of the stamps and post them here, we can tell you what era they're from.
The vintage drum market has its ups and downs, and right now its pretty much at the bottom. If you aren't in a hurry to sell, I would hold on to them, you never know what the values might do in the future. Do you have a child or young relative that might want to learn drums? Or learn yourself! Keep them in the family if you can. If you do decide to sell, post them here first, there are many people here who would love to give them a good home.