Google Fi data only SIM phone set up

I have 11 year old twins that want to ride their bikes around town and do a few things by themselves and want to have away for them to contact me if they run into any problems. I have Google Fi and remember seeing that you can set a phone up with a data only SIM and can use it with Google Voice number to still make some calls and receive messages. Anyone know how best to go about doing this or have a link to a guide? I also have a Microsoft 365 subscription that comes with 60 mins of Skype that could be used. Thanks