Would you leave a four month old baby for a week to go to mexico?

Long story short, my MIL has been giving us a lot of trouble basically since I got pregnant, and this morning she texted my SO asking if we would want to go to mexico with the family in January. I'm due in september and we tried to tell her we dont feel comfortable leaving our brand new baby for a whole week in a completely different country, and we also don't want to take him because he wouldn't be old enough to have all his shots. She doesn't care, shes pushing for us to go and "be part of the family". Its like shes forgetting we'll have a brand new baby. What would you do?