They would be happy in the ground for most of the year. Maybe you have a greenhouse construction project waiting for you in the future. Planting them in the ground in a greenhouse should work well for you. Especially one where you can remove the glazing in summer to help control temperatures better.
I just did an avocado graft a few moments ago, this is “Miranda Emerald Giant” (newly named by the owner, who gave permission to have us collect scionwood for the project I’m organizing) on a “Del Rio” seedling (seed was from Craig Hepworth, so definitely legit):
Those are my in-ground greenhouse avocado trees in the background.