Wasting money is forbidden in Islam and considered as one of the major sins, but if money is been thrown in the air then collected by children or participants in the wedding as a gift for them to make them happy, it will not be wasting money but gifting it to the children or participants. Gifting money should be within the moderate levels and not over the limits, otherwise if the amounts were over the moderate limits, or just for show, it will be then not permissible. If you know any part of the thrown money will be wasted, then it will be not permissible to waste any money.
Wassalam.