voy a tener hijos dentro de diez años (I'm going to have children within the next ten years) The future tense is used to say what will happen, eg: iré al cine con mis amigos (I will go to the ...
tener ganas de + infinitive (to want to), eg ... we will leave tomorrow). The future tense can be used to say what will happen if something else occurs, eg si hago mis deberes, saldré con mis ...