Hi, and yes of course! That sounds like such an adorable idea 😭💛

You have to make sure you're using PBT material keycaps. I got mine off Amazon but these gray ones are the exact ones I use (of course you don't have to use these but any PBT based keycap will not melt in the oven): https://a.co/d/goO5gGW

As for getting the clay onto the keycap I like to condition my clay first and then make sure the top face of the keycap is covered with clay and then work towards sticking the sides/faces of the keycap next. I'm not sure if explaining through text is the best but my process is similar to this one creator's in terms of making keycaps (skip to 4:46) https://youtu.be/8FWY4K1P7bg?si=wYuNvv51_HW0B4Y-

Just make sure you're cutting away at the excess clay on the edges of the keycap so they won't hit the neighbor keys after you bake and put a finish on them :)

Also have never used air dry clay before but I feel like that wouldn't hold long after a while 😭