Chlorambucil Risk in Multidog Household

Hi! My little senior (unknown age but 10-12ish) Shetland Sheepdog I rescued last year was prescribed chlorambucil after being diagnosed with Liposarcoma. He weighs 20lbs and takes 1.75 mg of chlorambucil a day. We just started our first dose today.

My question is, how worried should I be about exposure through waste to my other pets? I have the ability to make him his own quarantine space in the yard, but he is used to having full reign of the yard and I don't want him to spend whatever time I have left with him in a quarantine space without full enjoyment of the yard like he's used to. Obviously, I am concerned with the safety of my other pets. Two 50ish lbs mixed breeds, 10 and 13 and my 3 year old rough collie, 55lbs. None of my dogs eat poop or lick urine after another dog goes.

I'm considering using the quarantine yard as the 'potty' yard and letting him use the rest of the yard after he goes.

The advice from my vet was to pick up any poo as soon as he goes but that generally, UV from the sun wipes out any traces in urine pretty quickly, so she is not so concerned about exposure to healthy adult dogs, but to be worried if I bring home a puppy or if one of my dogs gets sick or otherwise immunocompromised. She also said that as long as he swallows the pill whole in a pill pocket and the pill doesn't hang out in his mouth before swallowing , it usually doesn't shed much in the saliva.

I've read some things online that go as far as to say pets in the same household shouldn't lick each other or share toys or bedding or water dishes. All of this would mean I would have to completely separate my Sheltie in the house 24/7 which I am absolutely not willing to do as that would be a major detriment to his quality of life.

Just wondering how crazy I need to drive myself to ensure my other dogs aren't exposed.