> just wondering how long it might take
It was probably a week or two before ours was fully settled. Just like yours he was fine going in but would 'wake up' and start shouting a short time later. The other time he'd make a fuss is if we put him to bed on his own. I would use their crates to give the puppy sleep time, and to give my other dog a bit of time out from having his tail chased and his head sat on!! The pup would yell if he went to bed on his own so I started to put them both in their beds at the same time then let my older one out once the puppy had fallen asleep. I'm generally at home all day and I didn't want to create a dog that couldn't be left so I would put the pup in his crate fairly regularly throughout the day to get him used to it.
It felt like this stage lasted ages but sleep deprivation bends time doesn't it?! Just grit your teeth and it will pass - it's worth it to know that the older ones are safe from the sharks teeth and that the puppy can't get into trouble when you're not looking.
Both my dogs have beds in other rooms too but I use their crates at night, if I'm out, or if they're wet. The doors are open most of the time and typically this is their preferred sleeping place if they want a proper rest; it seems that the other beds are fine for 'one eye open' snoozing but for real upside down, completely unconscious sleeping they put themselves to bed in their crates!!
Good luck :)