It is really hard to tell, as each dog is different & it depends on his genetics. Even though his parents are big, his granparents could of been smaller and he could of inherited the grandparents genes, etc..
A lab is not supposed to be too tall, Ussually by about 6-9 months of age you will see their full grown size (height anyways), although they can still fill out some.
Is he on a good quality puppy food?
you dont want too big of a crate until he is fully trained, so I would just get a crate that would fit him for a couple months, then go out & buy a larger one. But most crates that are listed for that breed should fit him just fine, you van always get one now, & just block off part of so he only has room to stand, turn & lay down.
sounds like a cutie! Do you have any pics? I havent had a puppy in a long time so a pic of his size may help me out a little more here.
good luck!