Oh boy! Lots of strong replies, as I might expect on this forum! Thanks for the feedback.
A bit of background - the female friend is someone I've known for 27+ yrs and who acted as a kind of mother-figure/ therapist when I was in my early twenties. We had our ups and downs over the years and I completely broke contact with her in my 30's because I found her very controlling and invasive and I was then becoming more autonomous and stronger in myself.
When I was PG, I got back in touch because I didn't have parents/ relatives who were able to offer me any kind of support for various reasons. She and her husband came back into my life and the twins' lives. However, we had a massive blow-up again when my DCs were about 8 months I think because she again did something that I found invasive and inappropriate - but, as she would see it, all with the best possible intentions.
After letters/ phone calls and then silence, we got back in touch I think about 2 yrs later and she and her husband began to take a grandparent-like role in my DCs lives. Not having parents (both are now dead) or extended family who are in any regular way involved, I was grateful that my sons had people other than myself who took an interest in them and appeared to love them and claimed to do so.
I think my friends believe that they DO love me and the twins but they are people who have v fixed ideas about things and find it hard to contemplate that they might be wrong and others right.
I've been hugely influenced by the female friend for so much of my life as she's been like a surrogate mother to me. They live in a city about one and a half hours' drive away. Initially, my DCs said they liked to stay with them as the friends gave them more freedom than I do (probably true) and do more exciting activities with them (probably true). It might be a bit like going to stay with grandparents or a father, in the case of the man, who does all the fun stuff, whilst mum does all the hard work at home.
However, DCs have become older and wiser and the son with Asperger's traits has particularly expressed feelings about not wanting to go to stay.
I continued to let them stay because I imagined that they were getting lots out of having other people in their lives who appeared to care about them, who showed them different ways of being and who did fun stuff with them. I WAS/ AM also afraid that my friends would get v angry and upset if the boys didn't stay. By the last time, however, I reduced the stay to one night, not two and after that one, resolved that the twins wouldn't stay again.
I foolishly thought I could hint at this but not confront it head on and hoped that they'd be like normal people and just accept that - whatever excuse I gave - it was time that the twins no lonegr stayed.
Since yesterday, there has been a long message on the answerphone from the man, saying how upset and angry he is, particularly as I've said to his wife that I don't want them to speak to the DCs about all this. He clearly believes also that the DCs WILL be going to stay again and that we just need to clear this up and for me to apologise.
He's said it's no longer possible/ convenient for me to call his wife, as agreed, tomorrow (when he's at work) as she'll be at hospital but that I should call tomorrow night instead and has suggested an inconvenient and late time.
So I've now just left another message for them to say I can't do that time but could talk earlier and that I DON'T think it's appropriate to involve the DCs.
I must admit to being in dread of the eventual call. These are people who won't let go, believing themselves to be motivated by love and care. They'll make a HUGE thing of it and may even turn up at the house sometime. I find it v hard to stay rational about this as they're what I describe as our closest friends who've stuck by me over the years. In many ways, they're the only 'family' that my sons have got - although they do have more extended family but we only see them about once a year at most.
Whilst some of the MN views expressed above are naturally v strong, it's helpful to hear them as a counterbalance to the part of me that feels like I've now done something wrong, that I have no power in this situation and that I should back down, give in and apologise!
I'm not a complete passive drip in most other contexts of my life BTW, although you wouldn't know it to read my OP!
But I do find that I tend to appease and please and become compliant with people in order to avoid confrontation, which I guess is what I've done here.