Spending the night in a motel

My boyfriend has been out of town working for almost 2 weeks. We wanna get a motel when he comes back so we can spend the day and night alone. And also, so we can have sex of course 😂 I’m 18 so technically I’m an adult, but my mom is very strict and I know she wouldn’t want me to go, plus she would ask a million questions. What should I tell her? Should I make an excuse? (Eventho I’m 18, I don’t think I should just leave without telling her since I’m still living in her house)