Guests under the age of 18 must be accompanied by a parent or guardian after 9 p.m. in Universal CityWalk on weekends* unless staying at a Universal hotel or planning to visit specific venues or events within CityWalk or the theme parks. Click here for more information. *Subject to change
https://www.universalorlando.com/web/en/us/plan-your-visit/hours-information/park-hours