Hi

Damjan
You 're right about easiness but somewhat further
should be taken care of.
It's how you improve performance.

Just my idea!

I think that when you convey the data serially.
Only 2 port is need for complete transmission
but if I were you I would disable or latch output
for protecting unexpected result.

Thus,it's necessary to use another Pin to control
this.

Some environment may not convinient to use many port
as you wish. I2C may be the best choice for that
situation.

If you are really free.Then Damjan's recommendation
is fairly good for cost-down your project.

Best Regards