Can multiple users track an AirTag?

Sorry, not currently possible.

The option to share AirTags with people within your Family Sharing Group will be available with iOS 17 when it is released later this year.

click here ➜ iOS 17 Preview - Share AirTags - Apple

No.

From: How to reset your AirTag - Apple Support

"An AirTag can be associated with one Apple ID."

Note that while Phil0124 is correct about iOS17 allowing multiple users, I didn't think it was likely your "assistant" would be part of your family sharing group so I didn't bother mentioning iOS17.