The short answer is that you should file a gift tax return (form 709), but you won't pay any gift tax or use any of your lifetime exemptions, because you and your wife can split the gifts 50-50, so that neither of you will have made a gift of more than $14,000 to any other individual.
Thus, each of you will be deemed to have given $9000 to your father, $5000 to A, $10,000 to B, and $2500 to C. Since all these amount are under $14,000, there is no gift tax or use of the exemption.
I am assuming here that both of you were in the US during 2016 for 183 days or more, long enough to be residents for tax purposes under the substantial presence test, and that the gifts were made after you arrived in the US.
Review page 6 and following of the 2016 instructions for form 709 for the details of completing the form for gift splitting. You should qualify to file only a single form 709, though you can file separate 709s if you want to.
