First, let's convert the 34 yards of streamers into feet. Since there are 3 feet in a yard:
\[ 34 \text{ yards} \times 3 \text{ feet/yard} = 102 \text{ feet} \]
Next, we will calculate the total length of streamers hung by Jerry and his dad:
\[ \text{Jerry's streamers} = 25 \text{ feet} \] \[ \text{Dad's streamers} = 38 \text{ feet} \] \[ \text{Total streamers hung} = 25 \text{ feet} + 38 \text{ feet} = 63 \text{ feet} \]
Now we will subtract the total streamers hung from the original amount in feet:
\[ \text{Remaining streamers} = 102 \text{ feet} - 63 \text{ feet} = 39 \text{ feet} \]
Finally, we need to convert the remaining streamers back into yards:
\[ \text{Remaining yards} = \frac{39 \text{ feet}}{3 \text{ feet/yard}} = 13 \text{ yards} \]
Thus, they have \( \boxed{13} \) yards of streamers left.