"We are going to sit here."
Translation:Nosotros vamos a sentarnos aquí.
Joel, the reflexive form of the verb sentar (to sit) is used here to emphasise that the sitting is being done by 'ourselves', the act of sitting down rather than being in a seated position. Saying 'nosotros sentamos' translates to ' we are sitting', the action already completed. Nosotros nos sentamos means we are in the act of sitting down.
I am not well-versed in this but I thought after a congugated "vamos a " you would need to use the infinitive verb sentar?