I agree with weedith, what Rumple did was to protect his son and any parent would have done it. Sure, some who might be braver than he was would have gone some other way and tried to fight the guards or something but Rumple was obviously not capable of that (not just the coward part but also the leg part, it’s a lot harder to fight with a limp). I also feel like even now Rumple wouldn’t harm children because he knows what it’s like to be a parent and kids remind him too much of his son.
He also didn’t give me any vibe of being cruel or capable of murder before he was cursed, that time he was talking about his wife he just seemed sad that she was gone and like he regretted that he might have had a part in her leaving/dying. If he was hiding anything I think it would be that she really did run away like the guard said.