Hip displasia??????????

my family has an american bulldog,did weigh 118,now he weighs 98,he was fat,but now hes lostg some and gained a lil bit of muscle,when we see all these other dogs running,playing and swimming we wish to god he could do that,hes not happy being sheltered,my mom and sister shelter like if they walk him for 5 minutes they say oh hes getting too hot we gotta take him in so he can cool off,they wont let him dig,which he loves to do,but i see why they wont let him dig because its still pressure on his hip,but they shelter him too much,he likes water(swimming),And he loves digging holes,hes been an inside dog all of his life,,,but how in the heck do i convince them to quit sheltering him so much,if i say something wrong like,yaw should quit sheltering him,just let him have fun,theyll say,dont tell me what i need to do,ill do what i want to he's my dog,,,,,how do i convince them to quit sheltering him,,,,and how can we make his hip better???