Thanks to everyone for reading and replying. I have an update but it's not much of an update. My son went back home (250 miles or so) after we decided we could not find any noticeable coolant leak. I test drove the car with my mom one day when I took her to the doctor and the check engine light came on. So I had them run the codes at Advance Auto and, to my slight surprise, it was to do with the fuel pump relay voltage, two codes. It reset after he pulled the codes and has not come back on again, so like the coolant, I'm not going to fix anything if it's not broken. I also saw how the car was holding good pressure in the cooling system because after I got it home I loosened the antifreeze cap on the reservoir tank and it hissed away at me with a good deal of pressure. My son's been checking the coolant but it hasn't gone down in nearly a week now, and everything is going just fine with the car. I'm still suggesting to him that he take it in for an alignment as I think it needs it after buying a new tire that was worn on the front driver side a bit more than the others. I'm going to make sure that he asks them about the check engine light and the coolant, and the dealer can make any kind of determination if they want to do anything under warranty, but of course the car is high miles and out of warranty now so this would have to be something covered under defects. Other than that the car is doing very well! I might not be coming back for a while because I'm not sure I can offer much assistance to anyone else seeing as I have not had to do much work on this car in the 118K miles that we've owned it since new.