lossening up my pinky finger

I'm an older guy (Retirement age) that has just decided to take up the guitar again after 40 years of not playing.

(I'm just a tad bit rusty) 

I've always thought I had big hands and long fingers 

But I'm having trouble getting my pinky finger to stretch to some of the notes. For instance when playing the pentatonic scale and stretching to the high "C" note on the E sting from the fith position it doesn't want to stretch all the way up there without taing my whole hand off the frett board and lumbering up to that note.

Other than just repetition and practice. Which I'm doing

Is there anything else I can do to lossen up and widen out may hand and fingers? 

This tutorial is aimed at improving finger strength & dexterity.

https://www.guitartricks.com/tutorial/1829/

This one does the same, but targets the pinky.

https://www.guitartricks.com/tutorial/1292/

Having said that, in some cases it's okay to use your ring finger.  Using one finger per fret is a good default setting.  But sometimes the musical context requires a different fingering. Especially when doing pentatonic scales like you mention, because you might want your ring finger available to do a bend.

For example:

https://www.guitartricks.com/tutorial/1614/

https://www.guitartricks.com/lesson/13754

Hope that helps!

Thanks a lot, I can also use this tips.