Yeah, I would be worried about our dogs ringing the darn bell ALL the time, just for fun! I taught Harper to play a toddler's piano, one of those tiny kids' things. Well, he doesn't play tunes or anything. LOL! But, once he realized he got a treat for tapping the piano keys, it was on! He plays ALL the time!
I would be careful in assuming that your puppy is "house trained" just because he can hold it through the night. Body systems slow down at night, heart rate, breathing, blood pressure, digestion, all that good stuff is on "sleep mode" so to speak, so less urine is produced. That enables dogs (and humans, for that matter) to hold it better at night than during the day.
Our puppies could hold it at night way sooner than during the day!
As for at night, you could try it on the weekend, as you say, and see how it goes, just leaving the crate door open. If that works well, you could transition to using a doggy bed. But, I wouldn't go straight to the doggy bed. A change like that might make it super obvious to him that things have changed, and he might get curious and decide to do some night time exploring. He's still very young and young puppies are very curious, and can get into a lot of trouble at night if left to their own devices!