In theory the answer is no, since the nutrients won't be up to scratch, but it's only a few days... My first cwpc gave me an out of date tetra though- I didn't realise until I went to drink it and it tasted really bad!!
Maybe if they taste ok, take a multi vitamin every day you have them just in case?
You can get the shaker from Your CWPC - I have 2 now so one is always clean whilst the other is in the dishwasher!