Here are a few options within walking distance to the venue.
Best Western Plus Suites Downtown
Ramada by Wyndham
Hilton Garden Inn Calgary Downtown
When eating out - consider a "good-better-best" approach that allows you to enjoy your plant-based plate when away from your own kitchen. This is a collection of suggestions to check out - remember to ask questions and make requests - like cook with water instead of oil, dressing on the side or substitutes for dairy, etc - you get the idea!
The Dandelion Cafe
Community Natural Foods 10 Avenue Market and Cafe
Gobi Grill (Marlborough Mall)