No, you aren't too old, as long as you can sound somewhat young.
Heres a table of what you should say:
All: Either "Hi, my name is (character name)", or...
Sonic: Let's do it to it!
Tails: Alright, Sonic!
Scratch: HA-HA HA-HA!
Grounder: So, what was our plan again?
Robotnik: I HATE THAT...