Cross Your Fingers -- Mine are
How do you handle this

Man, I'm glad I'm not an administrator

Here's the deal.  You have 3 teachers in teaching area 1 and one is retiring.  You have 4 teachers in teaching area 2 and none are leaving.  Both areas are electives.  You have to reduce head count because your school is downsizing.

So here are your choices:

Keep everyone who wants to stay at your school and move the students you can not accommodate in teaching area 1 into teaching area 2.

RIF a teacher from area 2 and hire a new teacher for area 2.  And here are your choices in the RIF:  You have two 20+ year teachers, one of which will probably retire next year.  Of course, she said that last year.  One has been in the school for three years, for two of those years his nickname was coach and he hasn't changed his teaching style.  The fourth is a very hard worker, and pitches in when she is needed.

In my opinion you're better off keeping what you have and know, rather than bringing someone new, especially since turn over is high in both areas.

Sadly, the people in teaching area 1 can't see the forest for the trees.

Like I said, I'm glad it isn't my job.