First, let's do an inventory of the words we need to insert into the paragraph. What do they mean?
Cenar = to have dinner
Deber = to have to, must
Desear = to want, wish, desire
Ir = to go
Then, we will look at the meaning of the various elements of the paragraph. For starters we have por qué (why), a no for negation, an a, and an infinitive cenar (to have dinner). The a + the infinitive cenar tells us that we should have ir as our first verb since ir + a + infinitive is a common pattern. Therefore our questions will be --
Por qué no vamos (nosotros form of ir) a cenar? (Why don't we go have dinner?)
In the second sentence, Miguel is talking to his kids and will use the vosotros form because he lives in Sevilla where this form is used. We have llevar (to take) in the infinitive (second verb) form and el perro a casa (the dog home). So, let's say --- Jaime and Miguel, you guys must take the dog home.
Jaime y Miguel, (vosotros) debéis llevar el perro a casa.
Elena y yo (Elena and I) will bring us back to the nosotros (we) form to say ---
We want to take Raquel to the hotel.
Deseamos llevar a Raquel al hotel.
Finally, at nine all (todos) of us (We all) have dinner in the Río Grande Restaurant.
A las nueve todos cenamos (we all have dinner) en el Restaurante Río Grande.