Hi and welcome!
Yes, knitcindy's advice is good about the weight for DK yarns and the result of using your yarn. Here's a chart
that may help to clarify the different weights, too.
If the pattern is like this one
, you could follow the directions for a smaller size and end up with a larger blanket that may be close to the size you want. Be sure to do a gauge swatch so you have an idea of the finished size.