Depending on your definition of part-time, but many companies in The Netherlands will allow for a 32 hours week (4 days).
As far as I know is hat not uncommon in Sweden either.

A seasoned good programmer will be easy to manage. They'll do the job and keep you up-to-date on things.

It's the young less experienced guys or the not-so-good programmers I would worry about. These are the types that are supposed to be "creative people" and refuse to be managed...