Hi Badger, Welcome to the site..
I think you would be OK the first year in them growing true to type...
The problem of cross pollination would occur if you wanted to save seeds off these for further crops
For them to be true and avoiding sports, I think You would have to grow each species in isolation..
Just shielding from bees would not stop them cross pollinating as this can be done by breeze.water spray and even tiny insects..I am no horticulturist, but this is my take on it .See what others think on here.. Jim