My SIL asked if we could look after her children next Saturday, didn't really want to (only because I know they'll be majorly over excited) but said I would. Today she text and said could she drop them off Friday night. She said it would be easier for her (obviously) as then she could get on Saturday morning. I totally see where she's coming from but I don't want them overnight. They don't sleep well and I am not feeling too good anyway.
Would I be unreasonable to say no to them staying overnight?