Unless the court order changes, Father will be with the 17 month old every Sunday am. To pm, whether it's mother's day, your birthday, your son's birthday, Christmas, etc.
18 months is fairly young to be away from mom for a long stretch, but as your kid gets older, you may want to consider getting a Holiday Physical Time Share Schedule (that overrides the regular custody schedule) such as:
Mother's Birthday (February 9) 3:00 pm to 6:00 pm with Mother
Father's Birthday (April 10) 3:00 pm to 6:00 pm with Father
Mother's Day 6:00 pm Sat to 6:00 pm Sun with Mother
Father's Day 6:00 pm Sat to 6:00 pm Sun with Father
Child's Birthday (September 1) 3:00 pm to 6:00 pm with non-custodial parent
Halloween (October 31) 4:00 pm Oct 31st to 10:00 am Nov 1st, even years with mom, odd years with dad.
Thanksgiving weekend 1st half 3:00 pm Wed to 10:00 am Fri Father odd years, Mother even years
Thanksgiving weekend 2nd half 10:00 am Fri to 6:00 pm Sun Mother odd years, Father even years
Christmas eve/day 1st half 6:00 pm Dec 23rd to 8:00 pm Dec 24th Father odd years, Mother even years
Christmas eve/day 2nd half 8:00 pm Dec 24th to 8:00 pm Dec 25th Mother odd years, Father even years