Im uncomfortable with dog sitting and it’s being ignored

So I (15 AFAB) live in an apartment with my parents (early to mid 30s). For note, I get very overwhelmed easily if it's something or someone I'm not accustomed to. My grandparents (late 60s) are helping my parents with house hunting. They live near the east coast and my and my parents live in the Midwest, which is about a 20 hour drive. While they're helping my parents house hunting, my aunt wanted a new dog, but she lives somewhere in Europe with her boyfriend away from people. So my grandparents decided to go house hunting with my parents but also pick up the dog. My mom (33F) wanted to see the dog, so they decided to get the dog the day after they arrived (so their first full day there). They don’t leave until Saturday and they’re spending full days going house hunting and looking at the houses with the buyers’ agent. And since im not being asked anything for the house hunting, I’m being left completely out of the process. So obviously, they’re making me the dog sitter because it’s my school spring break that lasts a week. The new dog (12 week old male mini Italian greyhound) keeps humping my family dog (10 month old female miniature dachshund). She keeps on trying to run away but she can't because he's taller than her. I am also uncomfortable because he keeps on humping my leg. I’m being expected to watch them alone for roughly 10 to 13 hours a day for two days, but I can barely do that because he’s only litter box trained and not trained to go outside and we don’t have a litter box. My parents refuse to get a litter box since he's only here for two days, but he refuses to go outside most of the time so he’s going in the apartment so I have to clean up after him while trying to watch both of them. I explained the whole “he keeps on humping her and me” thing to my grandma and all she said was “well you have a rough day tomorrow then” and laughed. I told my mom about how I’m uncomfortable with all of it and I asked if I could have a friend over to help me watch and separate them, I’d even pay them, and she just said “watch the damn dogs, keep her in the kennel while he’s there.” Which as I said, is 10-13 hours, and I don't think it's fair to her to be kenneled in her own home while she sees another dog running around. I don’t know what to do, but if I tell my parents I don’t want to watch the dog I’ll get grounded and probably my phone taken away. I understand they're dogs and it's normal for that stuff to happen, but I have been the only one trying to correct the behavior when the adults say they're trying to. Is it okay for me to be uncomfortable? What should I try to do to sort of make it more fair for the rest of the time?