Should I agree to have dinner at my husband's ex wife's house with her and her new husband?

Talk to your husband, tell him about your feelings and how you don't want to let the kids think his ex and him are getting back together. He married you for a reason. I ume he loves you and treats you well, so talk to him about it. His wife is a married woman as well, she moved on, so don't let it bother you. I don't know who broke up with who in the relationship, but both are now married, they both moved on. You are your husband's current wife. So even if they had a history in the past, you mean something to him. Talk it over with him and let him know your feelings.