For you, as the donee (recipient of the gift), there are no income tax consequences.
For your father-in-law, the only (likely) ramifications would be that he has to file a Form 709 (gift tax return), assuming the "sizeable amount" is more than $15,000.
See https://www.irs.gov/instructions/i709#idm140554828371904
Considering the fact that your father-in-law has "trust managers", he probably is well aware of the filing requirement.
