To be accurate, Eric Trump did not donate $16.3 million to St. Jude's he helped raise a total of $16.3 million over 10 years. He was certainly instrumental in the fund raising's success but not the only person who donated.
I know he’s been very involved in helping St. Jude’s financially. IIRC, during the campaign, he was bullied to withdraw from the charity in some way. As always, the Dems hate Trump more than they want to save the lives of children.