
Although I've never used a crate to housetrain, I find them invaluable when you can't be right there to supervise, so yes to a crate. Set it up in the room where you are most by day, cover top and sides and leave the door open so the puppy starts to use it as any other dog bed. When you have other things to do, play with him to get him a bit tired (!) and then take him outside to empty and back to the crate with some treats, shutting the door. He will probably complain but as puppies sleep a lot, should settle down for a nap. I'd be prepared to move it in with you by your bed at night although he may settle in the crate with your other dog there too, not in the crate! It all depends on the individual puppy. Some will happily accept being crated, some won't.
Make sure you correct the puppy if he gets too pushy with your older dog. Adults know not to attack puppies, but if they see you are in charge, he should settle down with his new buddy. With an older incoming dog, yes meet off the property, but if this is an unvaccinated puppy, you can't do that so you just have to do as suggested - be there to correct the puppy and use a crate.
Hopefully all will be well, but just as with humans, dogs don't always get along so there are no guarantees that this will work.