Shavuot is included among the three “Regalim,” when there is an obligation to rejoice and be festive. The Gemara states that according to all views among the chachamim, there is an obligation to enjoy oneself on Shavuot. Beyond the spiritual enjoyment that we experience by studying Torah, there is also a halachic obligation to rejoice through physical enjoyment. Chachamim teach that for men, this means indulging in meat and wine (in moderation of course). Although there is a widespread custom to eat some dairy meals on Shavuot, one should make a point of eating meat on Shavuot, as well. If a person does not enjoy meat and wine, then he should eat whatever foods and drinks he enjoys.
One is also obligated to make his children happy on Yom Tov. The Rambam (a”h) writes that this is done by giving them treats, candies etc. The mitzvah also requires making one’s wife joyous, and the Rambam writes that one should purchase new clothing or jewelry for his wife before the chag. If one’s wife does not need new clothing or jewelry, then he should buy her other gifts, even fine foods and the like.