Bladder Incontinence

I really need help with Carlos. He's turning 15 on the 23rd of Feb and the older he gets the worse his bladder incontinence is getting. I walk him and Arianna 3 times a day for 45 minutes but it still doesn't seem enough as just about every 3rd day I wake up to a bathroom, laundry room or kitchen floor covered in piss. I've tried diapers but he hates them and doesn't stop until he's managed to get them off.

I'm running out of ideas. Letting him sleep outside is not an option because it's cruel to make him sleep outside after having slept inside him whole life. I spend a ton of money on disinfecting products and I'm really worried that Arianna is going to pick it up as well. She was toilet trained from the day I got her at 4 months and has never had a single accident to date so I wouldn't want her to start now.

I can close the doors to the bathroom and laundry room but the kitchen is an open area and if I close my bedroom door at night, he's just whine until I let him out. I make sure to let him into the backyard every night around midnight to give him a chance to do his business and take them for their first walk around 7.30am.

What are my options here?