I was going to say the same thing as Jan!
Personally, I wouldn't be too concerned about the exact gauge since it is a blanket ... you could always cast on extra stitches to account for the finer gauge (just be sure your total number of stitches works with your stitch pattern).
I would NOT recommend a yarn that must be hand washed for a baby blanket though .... the yarn you found is lovely, but I suspect it will not hold up well at all as a baby blanket. And I know that I wouldn't want to receive a baby gift that has to be hand washed (if I did, I would never use it!).
Just some things to think about! You could try checking out the yarns section on Ravelry to find yarns that are an appropriate weight and are machine washable to see if you find one that you like and fits your budget.