I would definitely use a cot first. I know you can get rails for full sized beds, but they don't go all the way around and also are only about 40cms high so the bub is likely to climb straight over and bang their heads many many times.

I know my little man likes to climb the rails in his cot and I would be lost without them!

Godd luck, and there is no stupid questions, only people too ignorant to answer!