Guinea pig and travelling? Please Click me!?

Okay, every summer I go to my grandparent's house where we stay for (obviously) the whole summer, and then return back to our normal house. I plan to get one guinea pig(the second one will come later when I get enough money). I know it's not good since they're herd animals, but I can't help it. I'm lucky to get ONE. The ride to our summer house is about 1 hour or under. I have to bring my pig. We stay there for 13 weeks, and my cousins come too, so they can't watch it. AND I wouldn't trust them either. Their family got 2 guinea pigs (boy and girl) when their kids were younger, and whaddya know, they had a baby. SO, now they're stuck with 3 piggles, and the littlest child (kyle) decides to put the baby in a empty PRETZEL BARREL -WITH- TENNIS !!! Bottom line, Martin was killed. I'm so saddened by their parent's lack of responsibility. Anyway, that's where the problem is. I know they aren't supposed to travel, but how could I do this? I would pull down the last two seats (it's a row of 3) so that there was one seat for me and a big space for the cage. Should I put a towel over the cage and give my pig treats, or should I put it in a carrier?! Should I even hold it? AHH! This question is REALLY confusing, I'm so sorry. Thanks for the answers in advance.