Am I being unreasonable?

My MIL wants to have our children tomorrow. They are 21 months old and 12 weeks old. They are both poorly, snotty noses, coughs temperatures. Ive had a few sleepless nights with them (my partner refuses to wake up and help). His mum wants to take them out for the day and he thinks I'm being unreasonable for saying no. She wants to give me a break which I appreciate but I can't let her have them it doesnt feel right to let someone else care for them when they are unwell to take them for a day out when what they need most is to be at home resting snuggling and sleeping as much as they like. It wouldn't be fair for me to make them go out for the whole day when they arent their best and be a burden on everyone that's going. Also what if they just want me and I'm not there? I would rather spend how ever many days it take to get through this with them up all night and long days with no break than let someone else have them and they need me and I'm not there. She can have them anytime she wants just not when they are ill. Also shes never spent more than 30 mins with my youngest so shes not having her for the day for a while and definitely not whilst shes ill. (She's had problems feeding from birth so there is different ways to feed her and it can take upto an hour so until shes prepared to spend a few hours with me so I can show her and be confident she knows what to do shes not having her on her own for a whole day (she knows all this, just isn't prepared to spend time figuring it out). I can't let her take my baby knowing she doesn't know exactly what to do. Am I right in saying this or am I over reacting?