This is a difficult one when you have kids. Probably the biggest bugbear. Yes I agree you have to have the same considerations given to you that you are giving them. Are you happy with him babysitting your kids when you and your partner are out or are none of you ready for that yet?
You have to be clear and forthright in telling her how you feel about this, without it getting into an argument.
Obviously they are her kids too.
"The secret of life, though, is to fall seven times but to get up eight times"