It's my husband's 40th in a couple of months. Because we have two kids (one only 5 months and BF) and little parental support due to age/illness on the one side and the fact that my Mum lives abroad, we put thoughts of a weekend with friends in Manchester (ideal meeting point for friends dotted over UK)to one side. However, my Mum now lives here for half of the year. We asked her if she would think about babysitting our kids for about 4 hours in our hotel room while we go out in Manchester with a big group of old friends. Her accommodation and any expenses sorted too. She said yes and we invited all the friends, the majority are coming, looks like being a brilliant night. She now says she cannot do it as my stepdad has found a cheap holiday away, 'too good to miss'. She won't even have told him what she'd promised us, to avoid any hassle. He wants minimum involvement and she has to tiptoe around him to get to visit us anyway. Well to cut a long story short I then turn to my sis who lives in Manchester who had already told me she had a fixed arrangement to meet up with an old friend. I asked her to reconsider pretty please, try and get a new date with your mate, do me a massive favour etc but she won't and says I have to sort it out. I really don't have anyone else to ask other than friends who would wonder why they hadn't been invited to the do itself and take the hump. She told me I was using emotional blackmail and won't budge. AIBU?