You can configure Airtable to send an email using an automation with a Send Email action. You configure the template for the email in the automation itself. You cannot trigger the automation from a button field, but you can trigger it from a checkbox field or single-select field.
On the other hand, if you want a bit more flexibility in customizing the email after it is merged but before sending it, you can consider using my Email Table app. It works in conjunction with a Send Email automation by creating a record in an email table, for the automation to send. With this app, the templates live in special template records in the Email Table. Note: I am the author of this app.