During tharpanam and sraddha days one can accept thamboolam but chewing them is prohibited. When we happen to attend wedding during a tharpanam day and when we are offered thamboolam and as it is considered auspicious, accepting them will not be malefic.
We should consider sraddham as a revered occasion, try to avoid going out on that day and if by chance we are given thamboolam on that day, there in nothing wrong in accepting it. One should not accept any charities on that day.