Feeling guilty 🙁

Hi ladies. My son is 6 months 12 days. Tomorrow my husband and I are celebrating his birthday, nothing crazy, just a relaxing day with massages and dinner. My son is staying at his grandma's for the first time. She watches him while we work so we fully trust her. I just feel guilty for having my son stay there. I'm kinda sad and I know I'm gonna miss him. Its only for 1 night but we haven't been away from our son ever. I feel selfish and I don't like that feeling. 😥