How to transition my puppy from sleeping in a crate in my room, to downstairs in his pen.

Hiya! I’ve got a 5 month old English Cocker Spaniel puppy. He’s doing really well in his crate and sleeping and mostly sleeps through the night (only exception is, is when he refuses to poop right before sleep). I’ve got a knee injury and can barely walk up the stairs, and I struggle even more carrying him upstairs and downstairs every night and morning. He’s good at being alone, and I’ve let him free roam downstairs while showering or cleaning, and he’s had no issue with it. There have been times where he would be in the pen downstairs alone and he’d whine a bit, but than again if I leave the house and he’s in the pen he’s completely fine. I’ve heard that for some people, it helps just immediately doing it — no transition or anything, just change it up randomly and keep him in there and see. But I’ve also heard that a transition period is needed where I could put him in the hallway and see how he does there. The only issue I’ve got with that, is that my cats roam around and often are more active at night. He doesn’t care abt the sound of them scratching the litter trays, but they knock stuff over that does wake him up.

I don’t really know how to approach it, but it’s getting more and more difficult for me to carry him down the stairs (they’re very narrow and slippery and I’m scared of falling cause I already have nearly fallen down them with him in my arms before). I also think he’d sleep better without any distractions / any movement around him. He wakes up really easily in the morning when he hears me wake up. I always get really uncertain introducing something new to him, maybe even more nervous than he is to experience it. I don’t really know how to approach it. I wanna do right by him, that’s what my priority is. He does sleep like 7/8h next to my bed in a crate, but I really do wanna have him sleeping downstairs in his pen as the end goal.

Does anyone have any experience with this particular situation ? I would really appreciate some opinions / what helped for other people. Thank you in advance!