U can get cleaning sprays specifically for dog pee as it needs to mask the smell or they'll do it again. If its a painted surface shouldn't be a problem but if it's just wood I'm not sure tho I'd expect the woodwud have been treated. I'm sorry but I think this is really cute. He's marking it as protection from predators. He must know baby is coming soon. 🥰
You should be fine to clean it and use it since it's not the mattress!
If you have simple solutions wee cleaner that works to get the wee smell out and disinfects slightly. There's dog floor cleaner you can use that disinfects I'd put that on top after the simple solutions and then do a bicarb clean the day after this just to make sure it's all good. I have an intact male husky cross and it took me ages to get him toilet trained properly so used this method minus the bicarb to clean my carpet and it worked pretty well