Hello dapklp,
I world advise keeping the workflows 2010. The 2013 workflows are a bit different, especially with mail workflows. 2010 workflows function just fine in the 2013 environment, just not vice-versa. Specifically I office 365 if you try the 2013 workflow and your email domain is not joined to SharePoint, the workflows will fail with errors.
There are some useful changes in 2013, such as looping workflows, but I would try it on a test list or library before implementing across all workflows.
Hope that helps!
Bre