My 2DDs are now 10 and 13. We have been having them for weekends and more recently weeks since they were tiny. Admittedly they had each other, but we never had any trouble. First time DD2 stayed she sat up in bed and said "I want Mummy and Daddy". We just said she could talk to them in the morning and she went back to sleep. I think the trick is to keep them busy.Then they enjoy themselves and they forget to be sad.
Have a lovely time with your DD ethelbags. We have done cooking,make your own pizza, sewing, knitting, painting, visits to the cinema, zoo, farms, walks in the woods, cutting, sticking. Endless, 'Nanny McFee' etc, etc Just enjoy