You can go to a big box store and buy an automatic waterer for somewhere in the range of $20. I think I paid $30-something and got one that does two different settings for two different outs. They run on AA batteries. Then buy a drip irrigation line or a soaker hose (saw those for $5-10). Set it to come out and stay on, whatever schedule you want. Test it out ahead of time to make sure it works correctly and is watering them as thoroughly as desired. You should be able to not worry about your plants while you're gone and even for the rest of the summer. It's much easier, since they say it's better to water plants early, than trying to get up early on a work day.
Additional Way:
Okay, I didn't see your comment about not having water near by. I think you can still do the same thing, but in a different way. You can go on craigslist or I've been told some restaurants have them, and get a plastic barrel that didn't have chemicals in it. You can get anywhere from a small drum to a 275lb IBC tote. You simply put it one a platform, the higher the better, though the 275lb tote would weigh roughly 2200lbs, and then put a bushing on it. The IBC tote already has a drain installed, you just need the garden hose adapter. Once you have this installed, you can use the same automatic timer and hose setup of your choice. The pressure will drop as the water does, so you won't get as much water for the same amount of watering time, once you get toward the bottom of the barrel.
