Input on putting my dog down?

Our family dog, Scooter, was struck with vestibular disease last year. He's 14 years old and is on his last limb. He has a bad leg which makes his walking even more unstable. He somewhat drags it from time to time. He has accidents constantly and he can't be left home alone for more than around three hours because of it. He still eats and has a love for food, but yet a majority of the time he just looks depressed. Maybe it's because we can't give him constant attention anymore since we don't have time. His sister is extremely healthy compared to him and we expect her to last at least a couple more years. But the rest of the family is talking about putting him down. I can tell there's still some happiness left in him...but..I'm just not sure about anything. With the accidents, falling down, bad leg (which he chews constantly making it bleed), arthritis, and everything else...maybe putting him down is the best thing to do. I'm 50/50 on it. I love him to death and I can't imagine ending his life unnaturally...but then again, he's taking a toll on our family and I have no idea how happy he is or how much pain he is in...