My son (dependent) had 1099 of $74, but I could not include in my taxes since it is his UGMA. Do I need to file his own taxes to account for the $74 in dividends?

No, not if that is his only income.

Here are the filing requirements for a dependent:

"You must file a return if any of the following apply. 1. Your unearned income was more than $1,050. 2. Your earned income was more than $12,000. 3. Your gross income was more than the larger of— a. $1,050, or b. Your earned income (up to $11,650) plus $350."