Ami padre y yo iremos a la playa.

a) poder
b) ir
c) vamos

The sentence Mi padre y yo iremos a la playa stands for the simple future. We use the Spanish simple future to talk about what will or shall happen. It is also used if you want to talk about the possibility of what someone may or might be doing in the present. So iremos is the conjugation of the verb ir for the first person plural in the simple future. So:

Mi padre y yo iremos a la playa means My father and I will go to the beach.

who do the detectives meet in the cementery: ¿con quién se encuentran los detectives en el cementerio?