The are no quarantine requirements for visitors to Yukon from Canada or the U.S.A., but Covid-19 vaccination is required to travel by air in/to Canada. Testing is currently required for travel from the U.S.A., as outlined here:
Proof of vaccination is also required to access some non-essential services in Yukon (e.g. pubs and restaurants).
The workshop venue is large and well-ventilated, with a normal capacity many times the number of expected participants.