I asked my wife about Escondido and now she wants to go so this is what I got from Aerotucan this morning for both adult and child (mine are under 7, dont know what their top end is):

"The cost per adult one-way Oaxaca to Pto Escondido in March or July can be $1,884.40 or $2,000.40 pesos
and the cost per child one-way $1,726.06 or $1,830.46 pesos

and

The cost per adult one-way Oaxaca to Huatulco in March or July can be $1,934.28 or $2,050.28 pesos
and the cost per child one-way $1,770.95 or $1,875.35 pesos"

hope this helps.