I edited your post to remove your surname and the hospital name. You may as well be anonymous.
Hospitals have lots of toilets, not just the large ones in public areas. Most wards have a single user toilet you can use. So it sounds like you will be alright in one of those.
Donít wait till you need to go to find one, scout them out in advance.
Don't wait till you need a wee to use one. Go to a toilet well in advance, one or more times, just to get used to the different environment.
If he is in for surgery, you donít need to be in the ward or hospital the whole time, cos there is nothing you can do to help. Even when he comes out of surgery he will be out for the count. So go out for a walk, round the wards, to the shops wherever. During that time on your own, you can go to a distant toilet and take your time.
Allow yourself plenty of time in the toilet. You may be there for a wee, but as far as anyone else knows or cares, you could be in having a long dump.
Take a paper with you to relax and pass the time.