My vote(with your three choices), would go for the 17 MK IV. It's a nice little round, and if loaded with light HP or polymer tipped bullets, will most likely not exit if you hit the shoulders on a fox. If it does exit though, you're gonna have a huge mess of a hide. It should do great on the coyotes.
The 221 is also a very good round for calling, but it's gonna exit on foxes just about always, no matter what bullet or velocity you choose. My suggestion with it would be 55g SPs at moderate velocities(that's what I do in the 223). They'll exit, but the hole in the hide will be kept to a minimum.
On a "true" calling rifle, any barrel longer than 20" becomes a hinderance in my book. A nice light rifle with a barrel between 16", and 20" is right in it's element on a calling stand.
Just for the record, my primary calling rifle at the current time is a Ruger 77 Hornet. My load is 50g Sierra semi points at about 2400-2500 fps. This load is plenty for bobcats up to about 125 yards or so, but "usually" doesn't blow a big hole in a fox at normal ranges.
I also use my 223 at times with 55g Sierra SPs loaded to around 2700 fps. This is a very tough bullet, and again, gives similar results in the 223 as the 50g SMPs do in the Hornet.