First the bad news. Burt Lancaster is much too old for the part. Though they use a younger actor for much of Barnum's youth, when they switch to Lancaster, he's clearly much older than the character he's playing.
Now the good news. Burt Lancaster. He's great. No one else could play P.T. Barnum as well as Bur Lancaster. Thank God they overlooked the age factor and went for someone with the right soul. If you want someone to play the great Barnum, get a great actor. And they did.
The script is beautifully written. Because of that, even though the movie was obviously shot on a budget, it suffers not at all. Much as my kids loved it, this isn't really a kids movie. I mean it's good for kids -- they will like it -- but so will anyone interested in P.T. Barnum or 19th Century America. In other words, do not write this off as a mere kids movie because it's not.