Long Nute Change Interval Question

[budbon]

I am prepping everything for hydroponics this spring in Colorado. I plan on having 6-8 Dutch buckets growing tomatoes and peppers as well as some 4" NFT tubes growing leafy plants and strawberries. My question: in the fall we plan a 4 week trip visiting the New England States. If I use large enough containers, would the plants survive without replacing nutrients? Also what would be the chance the PH levels would be so out of whack it would destroy the plants? I know our timing is bad but the trip has been planned for some time.
These plants will be outside and I can get friends to harvest if necessary.
Any suggestions would be appreciated. By the way, I'm a hydroponic newbie.