The Story of the Treasure Seekers is the first of the "Bastable" series by E. Nesbit, an English author of children's books who is practically unknown outside of England. This adaptation is most notable for its excellent cast, including early appearances by Felicity Jones and Keira Knightley, an over-the-top bad-guy performance by Ian Richardson, and Peter Capaldi before he developed his more colorful vocabulary. (Most of the other players, both major and minor, will be immediately recognizable to anyone who watches British TV or movies.) There's not much plot, and there are so many characters that you don't really anchor to any (Camilla Power and James Wilby probably have the biggest roles), but it manages to be fairly entertaining throughout. Overall it feels like it would fit in well among the better of the live-action Disney movies of the 60s and early 70s.
Review of The Treasure Seekers
