Initially, there are 18 children at the sleepover party, with 11 children having blankets and 7 children having stuffed animals. This distribution indicates that:
- Number of children with blankets: 11
- Number of children with stuffed animals: 7
When Jorge arrives with a stuffed animal, the total number of children at the party increases by 1, making the total number of children:
\[ 18 + 1 = 19 \]
Since Jorge is bringing a stuffed animal with him, we must update the number of children with stuffed animals. Initially, there were 7 children with stuffed animals. After Jorge's arrival, the number of children with stuffed animals becomes:
\[ 7 + 1 = 8 \]
Next, we need to find the fraction of children at the party that now have stuffed animals. This is done by dividing the number of children with stuffed animals by the total number of children at the party:
\[ \text{Fraction of children with stuffed animals} = \frac{\text{Number of children with stuffed animals}}{\text{Total number of children}} = \frac{8}{19} \]
Thus, the fraction of the children at the party that now have stuffed animals is:
\[ \boxed{\frac{8}{19}} \]