I remember the first time I saw this terrific film. I was nine going on ten and living in Westchester County, New York, at the time. "Happiest Millionaire" was the Christmas attraction at Radio City Music Hall that year [1967] and it was a delight! The performances, particularly those of Tommy Steele, Fred MacMurray, and Leslie Ann Warren are all bursting with effervescence and energy, and the Sherman brothers' songs, if not up to their work on "Mary Poppins," (But, then, what could be?) are consistently pleasant and enjoyable. As the last complete film that Walt Disney was to oversee before his death, it's one of his best latter-day works.
Which is why I find the critical drubbing it's taken over the years, particularly Leonard Maltin's in his book "The Disney Films," so hard to understand. "Happiest Millionaire" is what many family films try to be today, rarely succeeding. I was given a video of it as a present recently and found it just as enjoyable as I did 32 years ago, if not more so. Plus, living in the Philadelphia area as I do today, there's the historical interest, as well.
In short, "Happiest Millionaire" was great in 1967, and even better today. If you can see it, by all means do. You'll be in for a rare treat and a hidden treasure from the Disney vaults!