[quote Alcemeg]Oh God, OP, sorry you are getting such a kicking here for no apparent reason.
I just discovered your other thread and have posted there too.
I have not looked after children for more than a few hours here and there and am just scared I'll get it wrong
I'd be cacking my pants too, and it's bound to be scary for everyone (not just you). But all relationships have to start somewhere and you have the best of intentions, so that's an excellent start.
It also sounds as though you and DP have an excellent solid relationship; I don't see any evidence of the exploitation and recklessness that PPs are being so bitchy concerned about. I'm sure you've expressed your anxieties to him, and there is no need for you to pretend to know all the answers. I'm sure he will help you to find the best way forward.
I know how hard it is to struggle with the idea of your own competence after an abusive relationship. You just think it goes to prove you never get anything right. Well, it doesn't. Sounds like you're in a really good place and will continue to get things right. Everyone makes mistakes now and then, but you have a good heart and your head screwed on.
I'm always posting this video on MN as it seems to apply to so many situations in life, but I just wanted to share it with you as a way to come to terms with your ongoing anxiety about screwing up.
Happy weekend to you and your lovely family! 
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Thank you, I read your comment on the other thread too. I just wanted to say you are wonderful and that was really, really helpful.
I've chatted with DP and have suggested that on Sat morning I'll make some plans with friends and go out till mid afternoon to just give them a chance to settle with just him and then we will go from there. We are both excited and nervous. I also took another piece of advice! I've thought long and hard whether there are any things I would be sad about if they got wrecked and bought a plastic table cloth for my dining table so they can go to town on that now
. So thanks.
I am really grateful for the helpful advice I received on this thread to the question I asked.
To those still concerned, both DP and I (and his ex actually) work in a profession which means we are acutely aware of safeguarding and also child development, which I mention just to clarify that children do decidedly not develop attachment disorders from visiting their dad (and his partner) to the poster who suggested as much.
DP is a man who as I said I have known for years through work and who even in hugely emotive, critical, difficult situations no matter how tired, stressed or worn out, is endlessly patient and has never ever lost his temper or so much as raised his voice to anyone. He is respected and well liked by everyone who knows him (even his ex who he has a decent relationship with despite everything). She also clearly has no concerns over sharing their care with him, neither has she been concerned about them spending time with me.