AITH for not liking the idea of my partner taking his disabled participants to our house or using our car to drive them around?

We are living in Australia. My partner is a disability support worker and works with a company supported by the NDIS. He's got a lot of freedom in his job, if his participants don't specify or have any whishes, he can do whatever he likes with them. One of his participants, a boy in his early twenties who has down syndrome and is non-verbal (possibly autism?), he likes to take to our house so that he can do house chores or relax while his participant sits on the couch and watches TV. I don't know how long they are spending time there as I am at work at the same time, but I think it's most of the morning. I'm extremely uncomfortable with it. I don't like having strangers at our house, especially when I'm not there. I don't like the idea of this boy, who also has poor hygiene, sitting on our couch and cuddling with my dog. The smell of sweat lingers in the apartment for a day after that even with air fresheners. I don't have anything against people with disabilities at all and I know that it is not the boy's fault or my partner's, as that is not a part of his duties, but I'm not happy with it and don't understand why my partner doesn't just go to his workplace with him and does activities there. AITH for the fact that I don't want my boyfriend to take his work home and let anyone in the house that I don't approve of? I haven't told him yet, because I am very unsure if I'm being unreasonable or if it's fair I think like that.

Another issue I have is the fact that he uses our car for two mornings during the week and first I didn't have an issue with it, one morning he uses it for the boy with down syndrome and the other morning he uses it for another participant. While he only takes the first participant from A to B, he drives the other participant around for almost 3 continuous hours. When I asked him why he said that his work doesn't provide him with any activities to do and whenever there is something to do, the participant declines because he only likes going for drives. We already had an argument about that because his work only reimburses him so many kms. Our car swallows petrol like it's nothing and I'm very sensitive about using our money (we have a joint bank account) for work expenses. But anyway, both participants have poor hygiene and smell really bad. They are sitting on the passenger seat and the smell stays in the car for days. I can't stand driving without having the windows down for a few days after that. I told him that I hate it when he uses the car for work, but apparently his workplace doesn't have enough cars, so he has to use ours for those two mornings. So I don't know what to do. I will definitely buy car seat covers so that I don't have to sit where they have been sitting, the thought of it even disgusts me. Again, it is not the fact that they are disabled, it's the fact that their primary carers fail to teach them proper hygiene!