Yes, especially if they are rated for that environment. Just make sure the watts of the amp are greater than the speakers. If you pump more watts into the speaker than rated for they will sound terrible and may ruin them. Connection is made via banana jack. Can get this on Amazon.
Banana jack
At the very least, run wires if you have open ceilings. Make sure you know where they are in the ceiling. If you choose to do this later, the wires are there and can be accessed later. Be careful of amp placement. You don’t want it in an area it will overheat in, or be susceptible to steam in a bathroom.
I love the idea of in ceiling speakers. Have them in my kitchen. Seemless way to listen to music. One way that makes it perfect is in the wall volume control. So you don’t have to control your amp at its location.
Volume control
The other options mentioned above are definitely worth a look. Wireless speakers are great. You can get Sonos which will allow for an all over the house experience. Amazon Echo can do this, but is limited to streaming services and does not work as a Bluetooth device. I have single Bluetooth speaker in my bathroom. Works great, just get one that is loud enough for you.
Would be really cool if the amp had the ability to drive two sets of speakers and you could place another set in a room near the bathroom, ie: bedroom or home office.