Thoughts on language for Intro to Data Science?
The biggest strength of R when it comes to Data Analysis is in its data visualization. As you've mentioned it is a more or less dedicated tool for statistical analysis. 

The thing with Python is that you can easily go a bit off course with the lectures because for Statistical Analysis you'll have to understand, install and work with different libraries/APIs for plotting (matplotlib/pandas/plotly) and processing your data (scipy/pandas again/numpy). These may take different approaches for installing and working with besides being tools on their own.

RStudio already sets up everything for you for the most part so you can just focus on implementation; if you happen to need something extra installing packages from CRAN is incredibly easy letting you do it from the script itself rather than opening a terminal with conda or pip or whatever.

My notes:


If your interest is teaching more Data Science, as a tool in itself, go with R. It will let you focus more on concepts which are general.
If you're interested in teaching General Programming as a tool for Data Science and maybe other things, go with Python. 
If you like both ideas, I'd start with R and replicate results with Python later to show its integration with different tools. This way your students will see both approaches are feasible in the case they go out there and see it in the job market.