I think there are benefits to doing it both ways.
We had a team meeting today and someone asked if junior people could go to the senior stuff if they wanted to.
Of course, if there's space, that'd be OK I think. Some people learn well that way, being in over their head.
I kind of like the idea of doing them on two different days. It means people can optionally commit to only one day if they want to do something. It also gives you more time to dive into topics.
For the OpsSchool content, I'm thinking about targeting either very junior people who have very little or no Ops experience, or people who are about to fall into Ops (maybe developers who need to learn to do both).
I'd love to help people bootstrap a career, especially those who enjoy Ops type work, but don't know how to get a job or which skills to learn.