Is there a "ir + gerund" structure in Spanish?

Question

I saw these two sentences on YouTube:

por que no se van sentando? (Why don't you sit down?)
por que no van poniendo la mesa? (Why don't you set the table?)

I checked it out on the dictionary, and I found this explanation and example:

(used in progressive constructions)
a. to be
Voy planificando la fiesta. (I am planning the party).

The sentences above doesn't fit the description given on the dictionary. I'd be glad if someone can explain this usage, please. thanks.

Answer 1

These two sentences:

• ¿Por qué no se van sentando?
• ¿Por qué no van poniendo la mesa?

actually seem to me to be better examples than:

• Voy planificando la fiesta. (which needs more context to illustrate the meaning of the verb phrase)

(1) "ir" + -ando/-endo can be used to refer to the way to go somewhere (a rather literal usage)

A. ¿Cómo vas a la escuela?

B. Voy caminando (I go on foot)

But it can also have (2) a more idiomatic use to refer to a gradual process. A typical example is:

• Vayan terminando (in Spain: Id terminando) meaning: Get finishing.

"Nos vamos sentando" thus suggests more gradualness, and is softer or more polite than the more direct "sentémonos".

"Vamos poniendo la mesa" is more gradual and less straightforward than "pongamos la mesa".

"Voy planificando la fiesta" seems to suggest that I am taking a series of steps leading to the final planning of the party, for example: Mientras ustedes deciden a quién invitar, yo voy planificando la fiesta (while you decide who to invite, I gradually make all the arrangements for the party).