Consider using a student as the person controlling the iPad when presenting the lesson to the class. It models the "driver-navigator" protocol for the students.
Consider not allowing students to choose their own Sprites. Limiting student choice in the beginning will keep the lesson moving but allow them time to play and explore when time allows.
Based on Scratch Jr. official lesson - Drive across the city.
(CCSS.Math.Content.1.MDA.1 : Using grid,
Similar to official Scratch Jr. lesson on Conversations.
Use Hide and Show blocks (under the look menu to code character animations and add to the story.
Written by Dax Smith, Sarah Breton, and Rick Bush
Find the official Scratch Jr. Lessons here.