If you expect people to create accounts on Wikipedia or other projects at an event, please read this: https://meta.wikimedia.org/wiki/Mass_account_creation#Requesting_temporary_lift_of_IP_cap

There are some automated anti-sock-puppet systems that prevent people from creating multiple accounts on the same day from the same computer or IP address. This can be a big problem if you have lots of new editors at a workshop, and everyone tries to create an account.

You may be able to avoid this by asking attendees to create an account in advance (but then they have to remember to do it, and to bring their usernames and passwords to your event). Otherwise, your best bet is to follow the directions on Meta about getting a temporary exemption for your event.