18 weeks and 2 year old going into surgery

Hi!! I dont post Alot but I'm hoping for some advice on what to bring with me/ if anyone else has had their kids go through it... I'm 18 weeks along and this week I found out my 2 year old Son needs a Bad Inguinal Hernia repaired and has a fluid build up taken care of as well at Primary Childrens Hospital which Is about 4 hours away from where I live..I just dont really know what to bring with us I've travelled alot with my kids but never to go sit in a hospital and never not being able to feed him for over 12 hours prior... I'm obviously a stressed mama here....