James:
If the script you show above is all you are doing, then you don't need the jquery-migrate and spjs-utility references. Those have nothing to do with SPServices.
I'd also suggest that you update to SPServices 2014.01, as the version you are using is quite old.
Shouldn't you be using SPCascadeDropdown for this rather than the functions you have?
Once you'd done that, let me know if you're still having problems.
M.
If the script you show above is all you are doing, then you don't need the jquery-migrate and spjs-utility references. Those have nothing to do with SPServices.
I'd also suggest that you update to SPServices 2014.01, as the version you are using is quite old.
Shouldn't you be using SPCascadeDropdown for this rather than the functions you have?
Once you'd done that, let me know if you're still having problems.
M.