advice

Hey ladies, I need some pep talk. So I'm 19 and my boyfriend is 31. Although there is a age gap between us. We've learned to Laugh about it instead of finding it creepy lol anyways he has three kids. They are coming up for the summer, and I don't know how to prepare my apartment or myself. I don't know how to say no, much less to his kids. I've never met them, so the first time we will be meeting is when they come up for the summer. Any advice on how to go about all of this?