Welcome to the English Magical Vacation fansite.
This is a Gameboy Advance game, made by Brownie Brown and published by Nintendo. It was released in Japan in 2001, but sadly an English release doesn't seem to be happening.
It's an excellent RPG with the most gorgeous graphics and music possible on the GBA.
2005-12-07: Added screenshots of Magical Vacation - When the 5 Stars Line Up from Famitsu to the Magical Vacation - When the 5 Stars Line Up page
2005-10-05: First Screenshot of Magical Vacation 2 for DS now tentatively titled Magical Vacation - When the 5 Stars Line Up.
More info on Magical Vacation 2