I googled and tried testing it - even using the email address of the cell phone that will send a text to the phone (ie [email protected]). No luck, not that I expected it, just was curious. I haven't used GroupMe's calendar function too much and other sporting team app options such as teamsnap probably have similar limitation (probably worse as they are mostly email driven).

At this point, the solution all depends on who the recipients are. I would guess that either they won't share their email address or just don't have one. The former could be done by creating a GroupMe group for just those people (assuming they are tech savvy enough to understand why it's being done). The latter may be easiest just to copy and paste the calendar information into a group text or teach them to get an email address (which could be challenging as well).

Not very helpful, I'm sure. Sounds like you know enough to have surpassed my expertise.