All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.

Dear brother in Islam, we commend your eagerness to become well acquainted with Islam and its teachings, which is the way Allah has chosen for the welfare of His servants.

First of all, we'd like to stress that in Islam, the `Eid is a day of joy, thanksgiving, worship, brotherhood, solidarity, and morality. A Muslim should take advantage of this day to bring himself nearer to Allah, Most High. Muslims should enjoy the `Eid in a lawful way and contribute to bring happiness and cheerfulness to all Muslims particularly, children on that day.

As regards your question, the eminent Muslim scholar, Dr. `Ali Jum`ah, Professor of the Principles of Islamic Jurisprudence at Al-Azhar Univ. and the current Mufti of Egypt states:

Muslims are permitted to have a happy time and enjoy the `Eid with customs including permissible forms of dancing, singing, and beating the tambourine provided that there is no mixing between men and women. When Abu Bakr (may Allah be pleased with him) entered the house of the Prophet (peace and blessings be upon him) on the day of `Eid, he found two young girls playing music and singing. Abu Bakr (may Allah be pleased with him) asked them, "Are you doing this in the house of the Prophet? How come?" But the Prophet (peace and blessing be upon him) told Abu Bakr (may Allah be pleased with him) to leave them, for `Eid is a day of merriment and joy.

`A'ishah (may Allah be pleased with her) was allowed to watch the Abyssinians do their war dance in the mosque. Imam Muslim reported on the authority of `A'ishah: “Some Abyssinians came and gave a demonstration of armed fight on the `Eid day in the mosque. The Messenger of Allah (peace and blessings be upon him) invited me (to see that fight). I placed my head on his shoulder and began to see their sport till it was I who turned away from watching them.”

There was a person known as "the arrows player" who used to make a demonstration by playing with arrows. Nu`ayman used to move the Prophet to laugh and smile with his funny words and movements.

Therefore, there is nothing wrong with wearing a certain dress that makes the children happy and cheerful, particularly on the day of `Eid. As for the history of the dress of a clown, it appeared in the West but there is nothing wrong with wearing it for Muslims on such happy occasions as the two `Eids.