How many songs are typically played at the Ceremony?

No-- that seems about right, though you may also just want some background songs (like 15-20 minutes worth) for when the guests are arriving and being seated.

You can skip the music during the unity sand celebration. In my ceremonies there is only about 30 seconds when the couple is actually pouring that music wouldn't be drowning out my explanation of what is happening.

We have a long sand ceremony. My FH has two children, I have one and we have one together. Each child will be pouring their own sand then us. So a song would fill the silence

We're going to have a long piece for while people are being seated, and it may double as the music for the WP and family entrances. Then I will have my own song. Then exit song. Then another long piece (or even the same one) as people are being ushered inside for cocktail hour