User blog comment:CNBA3/Episode 222 Review/Rantish/@comment-173.50.120.100-20150228142625/@comment-7418318-20150301084226

In this very episode Mira taught us that transforming into something completely different like animals is "level 3" and thus much harder to do than transforming into something very close to your own original body.

That Macao was able to transform himself into a lizard and perfectly emulate Natsu's voice shows that he's not just an amateur practitioner but an expert in Transformation Magic. Altering his body into a younger appearance (which would fall either into level 1 or 2 depending on how extensive the change is) shouldn't be a problem for him.