Well, it fits, but there are two minor problems. Duolingo tends to trade formal word for formal word and informal word for informal word, and are more likely to accept "grandpa" for "vô" or "vovô" than for "avô"; also, even if the "himself" bit is explicit in the Portuguese "se", it is not quite as natural in English. If that is something you would say, though, you can ask for it to be accepted.
This verb can mean "lift", "raise" or "get up" so when you hear "Meu avô levanta" without an object a possible doubt is "What does he lift?", however, this verb is so common that leaving out "se" (himself) wouldn't cause any confusion particularly with the addition of a word like "cedo" (early).