Pretty much my favorite unit to "have fun messing" with. Have an idea? Try it out! Their strengths I'd play to though are:
Feigned Fleight/Swiftstride: The rules make fleeing awesome for Terradons. Since they FLEE on the best 2 of 3D6, unless their being charged by a cav unit with high movement, they should be able to avoid overruns most of the time (statistically at least). Then when they rally (Cold-blooded RULES), they can MOVE on the SAME TURN! You can bait the enemy into missing his charges, mess up his battles lines, and then turn around and fly 20" the other way while your bigs slam in and rape face.
TIKTAQ'TO: I know people don't like characters, but this guy makes your terradons beast. If you can field an army big enough to use him, he can lead a Terradon unit, has higher leadership, and is a LITTLE less squishy than the other riders. Oh... and his mount gets killing blow (eventually). Using him to bring in a squishy unit as reserve, to any table edge, late in the game could protect the points while giving you an advanced look at your opponents strategy. One of my favorites flavor wise too, as he was a major part of backstory battles.