Do you have a full itinerary of where you'll be in Cuba?
https://www.etecsa.cu/es/salas-espacios-publicos has a list of places
where you'll be able to find WiFi in Cuba (you need to pay for an access
card which has a username and password on it, according to
https://cubasbest.com/wifi-in-cuba/ ).
Your group may end up going through the same struggle of getting internet
access and will probably have advice. If your group needs you to be
online, getting a SIM card would be the easiest, but, hopefully, it won't
be required. In any case, https://cubasbest.com/wifi-in-cuba/ suggests
that you should assume that you will not be able to access the internet,
but, if you do happen to be able to, then just consider it a bonus.
Note that you'll need to be able to turn on and off the WiFi in order to
save minutes when you do connect, if you are able to connect. Just pull
down from the top of the screen to turn WiFi on and off using the icons.
And, obviously, you'll need to carry the access card (with your username
and password) around with you.