Jewish Holidays

I run a camp for children under bar mitzva during a period that includes the Nine Days. We usually take them on trips off campus once a week. Is it permitted to do so during the Nine Days?

I live in a predominantly Ashkenazic community where the “Three Weeks” are observed with no music, and certainly no celebrations or weddings. A Sefardic family in the neighborhood has scheduled a wedding during the Three Weeks.

Is it permitted to make an engagement party during the Three Weeks (i.e., before Rosh Chodesh Av)?