Should i encourage husband to talk to his father again? or leave it be?

FIL and i got into an argument a year ago after he was rude to my daughter, he asked me to leave his house, so i did. he never apologized to her or to me. he continued to speak to my husband but refused to attend the kids birthday parties. my husband invited his parents to attend a very important function and his father typed a letter to him telling him how awful i was and how i was hurting the kids (our kids) and told him that he would no longer speak to his son. he also said we were treating him like a child molester and his mom agreed (he babysat our 5 year old daughter for us theday we argued) and said i needed to apologize.. i emailed an apology saying i was sorry he was offended and that i didn't want them to have problems with each other.(i do not even want to try to like FIL now) husbands parents still refused to attend. husband is still speaking to his mother but father is still refusing to speak to him. they are not doing anything to fix the situation or try to talk about it.