I wouldn't, because if their father shows no interest, then what kind of relationship will they actually have if you force it?
My daughter's father and I broke up when she was a bit shy of being 3. At 3.5 he moved overseas and never saw her again. He called occasionally, but those died off not long afterwards. There were periods where she'd cry about missing him, (and I'd spend my time wishing I'd hear news of his horrific death... how dare he cause my child pain and all of that...), but there was really little I could do. Trying to force him to be a part of her life wouldn't lead to more heartbreak... because eventually he'd just give up and my nagging would get us nowhere. Plus, if he's the kind of douche who treats his kids like that, then why would he be good for them anyway?
So really, I would cuddle him, NEVER bad-mouth his father, let him have his cry... he will be okay. If he gets older and wants to locate his father as, say, a teen, I'd help, but warn him that it may not go as well as he might hope.
]I think counselling may help too, if not now then in the future. Even just seeking advice from a counsellor... you're not going to be the only parent to go through this so hopefully someone professional has some useful advice.