Ex wife visiting with kids! HELP😭😭!!!!!

My SO and I live together in a different country which is like 8 hours flight away from where his ex wife and kids live. They have 3 kids together 9, 10 and 14 year old. He wants his kids to visit him here and since they cannot travel alone, they are coming with their mom. They are going to spend a week here and live with us in our home. I don't like the fact that his ex wife will be living in our home. The kids can come with their Nanny but my SO prefers their mom. NOTE! My SO never wanted to divorce but his ex wife insisted they divorce cos she has found a new love. His ex wife is beautiful and very attractive so he says n I know she is cute cos I have seen her pictures. I don't want his ex wife around cos I m afraid she can manipulate him if she wants. I don't know if I m overreacting or being paranoid. If he will bring his ex wife to our home, I will pack my stuffs n live which is going to hurt me 😭. Please how do I handle this? I m so confused.