If you are going to see a guy and want him to spend the night I would make sure that you are at least dating for about a month and your kids know him. It would be a bad idea to spend the night on the third date or a week into dating this guy. Serious relationships last longer when you take your time.
IDK I have been seeing someone for about a month now...we talked about it and we agreed its not time to be staying over yet...we are both kinda trying to take things slow...so I cant say, its the first guy I have had a relationship with in a yr of taking time for myself after my breakup...I guess just whenever you are ready and the little ones aren't there.
When your ready, your ready but I wouldnt involve the kids until they are ready. With my last relationship he started off spending the night when the kids were gone and then we waited until the kids were comfortable around him and starting asking him to stay before he would stay the night while the kids were home.