Warming up your voice for the day can help to prevent vocal strain, vocal fatigue, or other voice problems. Here are three exercises to do together every morning for ~2 minutes:

Loosen up with a few shoulder shrugs, shoulder rolls, and exaggerated chewing.
Do lip trills (like making a horse sound with your voice on) in a comfortable pitch.
Slide your pitch up a little and then down a little, 6x each: “hee,” “hoo,” “hoe,” “ha.”