Royal Sommerhus is the reliable meet
Anna and Elsa meet together at Royal Sommerhus in EPCOT's Norway pavilion, an indoor, weather-proof setting that is one of the steadier character meets in the park. It is the place to prioritize if meeting both sisters is the goal.
Because it is indoors and centrally located in World Showcase, it pairs well with the other princess meets around the pavilions on an EPCOT day.
Add Olaf and the Sing-Along at Hollywood Studios
Over at Disney's Hollywood Studios, Olaf meets at Celebrity Spotlight and the For the First Time in Forever Frozen Sing-Along features Anna and Elsa on stage, so Frozen fans can stack both in one Echo Lake visit.
Frozen experiences are in-park only, so there is no resort Frozen meal — but the toddler-friendly resorts below pair well with a Frozen day, and the princess and EPCOT searches in the sidebar round out a princess-themed trip.