If these projections hold, How to Train Your Dragon could score the fourth-largest three-day opening of the year so far, narrowly edging out Marvel’s Thunderbolts* ($74.3 million).

A live-action sequel, “How to Train Your Dragon 2,” is already set for 2027. Parents with young kids also continued to fill seats for “Lilo & Stitch,” which collected $31.1 million from 52 ...