My piggies don't like being left at all. I've once left them from 9am and then returned around 12 the next day. When I got back their cage furniture had been turned upside down, and they had obviously been very agitated as I could tell everything had been chewed alot. I did leave extra hay, nuggets, water, and I gave them a really generous veggie helping the morning I left. However, it isn't just about the food, or warmth (I left mine in September, when it was still quite mild), I think they just got lonely and worried without anyone around for that long.
Could you not just take them with you in a cardboard box with holes in? or a cat carrier, if you have one? And maybe buy one of those ball pits from ELC as a temporary cage? It wouldn't be too heavy to take with you. Just pack a small amount of hay, nuggets, a hidey, and their water bottle.