It sounds like you may be dealing with a behavioral issue here more than a medical one. Change can be very stressful, particularly for older cats. If they are urinating on things that are new to their environment (bags, boxes, etc.) but still also using a litter box, then they are marking to make this "new" environment their own. You can reduce this stress by getting things in order as soon as possible and then leaving things alone so they can adjust to their environment without a lot of rapid changes all the time. If you need to subsequently rearrange things, don't do it all at once. Every time you do this, from your cats' point of view, you are changing their environment and they will feel the need to deal with it as though they have been moved again.
So you want to find them a good vet? Well first of all any vet you go to....make sure that they don't just want to put them to sleep. All cats deserve a chance at life even if they can't pee in the box. Make sure they do all they can to save the sweeties. I would look for vets that have good reviews online. I hope this helped!