Exes and children visiting dilemma, what is your fix?

What would you have told or said to this young man? I knew this young man I will call Eric (to hide his stupidity) many, many gals found him to be devilishly handsome; which he used to full effect. He was certainly not smart to spread his conquest miles upon miles apart. So he ended up with some kids, then about 3 years later more kids. To make matters worse the mothers knew each other; both were exes and they hate each other with a passion. When ever a major holiday comes, Easter, Halloween, Christmas etc he gets the blues big time. His ex the mother of the older kids say he should be with them because they were his 1st. The mother of his younger children said to him that he should be with them since they are toddlers. Doing combined activities is a no go (he tried and it was like trying to put paper and a flame together in the same barrel) there is no peace between the mothers. What would you tell him to get the best result? Go with the younger, go with his 1st set of older kids, none of the kids, or just take the grief because it was a situation of his own creation?