Hello everyone!

First time doing Mt Whitney and am very excited. We have a group of 3 experienced Hikers and will be doing an overnight on June 17th. The only back pack I have is a 50 +10 L deueter bag that ways 4 Pounds. I am just curious is this is way to much and if I should buy a much smaller 1 to 2 day back packing bag. Thank you very much!