Send correspondence via text message in addition to email.

It would be nice if guests/potential guests could opt to receive all correspondence via text message in addition to email.  This would prevent the loss of communication that happens when emails are directed to spam folders.   

I'm afraid this is fundamentally impossible.  That's because the capabilities of SMS text messaging, email, and for that matter, channel internal messages, are very different.  So it is not possible to simply convert messages of one type into another automatically - that's why we have three completely separate template types, so you can best use the attributes of the different types of messaging.

If you wish to send messages predominantly via SMS, you can certainly do so by setting up SMS-type templates for all common messages.

Is it already possible to send a text message when an email event has happened to let folks know that they've received an email from me?  Thank you!

Yes and no.

There is no "just sent an email" event that could be used to trigger an SMS message.

However, you certainly can configure parallel messages, in SMS and email, and have triggers configured to send them using the exact same criteria and thus at the exact same time, which would more or less create the effect you're looking for.