Storing BM for a wedding

sneakersandstilettos19

Hello,

My sister is getting married Saturday and my MIL is coming to help with our 2 month old DS.  I will nurse him whenever I can but he will probably get a couple bottles.  Since I'm in the wedding and he is fed on demand it's hard to know if I'll be available to feed him when he needs to eat.  I have frozen BM stashed.  My ? is, should I thaw it and send it in the cooler bag with MIL or send it frozen?  I know it has to be used within 24 hours after it's thawed and I don't want to waste it.  

It's so much easier just to nurse him... Thank you for your help!