Hi
Intro
An Apple Watch Series 3 (GPS + Cellular) could potentially be used to help locate your husband, but keep in mind that various caveats apply to its use for that purpose. I have provided provided some introductory information below about related Apple services.
Consider also whether the device may be overly complex from a usability point of view for your husband (including potentially interacting with it accidentally). You may find that a purpose-built tracking device is better suited for your joint needs.
You may find it most helpful to visit an Apple Store and discuss your requirements in more detail. If buying an Apple Watch from Apple, free personal setup is also available to help you configure and start using it.
Location sharing
Setting up Family Sharing and adding your husband to the family group would, with relevant sharing permissions, enable use of the Find My iPhone app on your iPhone (or via iCloud.com in a web browser) to locate his devices, including an Apple Watch Series 3 (GPS + Cellular):
With or without using Family Sharing, Find my Friends can be used to locate contacts who have agreed to share their location with you.
If a contact is wearing an Apple Watch Series 3 (GPS + Cellular) and does not have their iPhone with them, then their location will be tracked using their Apple Watch. Location is only sent when someone requests to see it (it is not transmitted on a regular interval). Features of Find My Friends on iPhone include the ability to request a notification when a sharer next leaves their current location:
Various caveats apply to the availability and accuracy of Location Services information (whether via Find My iPhone or Find My Friends) when used in conjunction with any Apple device, including Apple Watch and including in respect of signal coverage. For example:
Examples of battery life on Apple Watch are detailed here:
Apple Watch - Battery - Apple
For the best battery life each day, it can be most convenient to charge Apple Watch nightly, overnight, being sure to follow Apple's safety and handling instructions when doing so. The battery will not suffer any harm from regular charging. Charging will stop automatically when the battery is fully charged and start again if and when required due to ongoing battery usage:
Device requirements
Whilst more than one Apple Watch can be paired to a single iPhone, only one of them can be active at any given time. For your husband to use an Apple Watch as his own, he would need a compatible iPhone. For Apple Watch Series 3 (GPS + Cellular), an iPhone 6 or newer model is required, running the latest version of iOS:
Set up your Apple Watch - Apple Support
In order to enable the built-in cellular capability, your husband would need a service plan for his iPhone that specifically includes support for Apple Watch Series 3 (GPS + Cellular), including the carrier activating the Apple Watch on the plan.
The Apple Watch would then only use the built-in cellular capability if it could not connect to the paired iPhone or, as a fallback, to a compatible, trusted Wi-Fi network:
About Bluetooth, Wi-Fi, and cellular on your Apple Watch - Apple Support
More information:
Set up and use cellular on Apple Watch Series 3 (GPS + Cellular) - Apple Support
