Why do they still depict the heroes as kids whenever there's a time jump? For example, Neil Armstrong apparently landed on the moon as a preschooler.
The Secret Museum's technology is so sophisticated, it may alter the children's perceptions to help them relate to the historical figures they meet, by making their adult selves appear child-sized. This might also explain why so many of the male historical figures are depicted with facial hair even in their boyhood, and account for incongruities of clothing like Armstrong wearing his space suit decades before the suit was manufactured: the Museum makes their child-selves resemble whatever photos or paintings the trio have seen of those figures as adults.
I thought it was actually more so for audience convenience, as the audience wouldn't really recognize them if they were shown as kids, so they could look like their childhood selves to the Xavier, Brad, and Yadina but look like miniature adults to audience. To be fair, we don't see a lot of pictures of the historical figures as kids but we do see a lot of their pictures (or portraits) of them as adults, though, a few of them (Helen Keller, Zora Neal Hurston, Florence Nightingale, and Jackie Robinson) looked more like they might have as kids. However, the perception filter could be when we're supposed to see them as adults
As of Season 1, the crew has twice encountered Amelia Earhart - Once in "I Am Amelia Earhart" and again in the "I Am Madam President" movie. Why is it that on both occasions, they act like it's the first time that they've met?
How come the crew doesn't get weird looks when meeting historical figures (since they look, well, different from the time period they're in because of their clothes, the way they speak, etc.)?
Maybe Berby and the Secret Museum's tech casts a Perception Filter so the kids don't stand out too much.
Even that wouldn't account for why three strange children inexplicably popping up in inaccessible places like the Space Shuttle mid-flight, or secure locations like the White House or the palace of the Pharaoh, doesn't cause a fuss.
