I do think it's a bad idea. I always think it's a bad idea to do a love spell on a specific person. When a relationship ends, it ends for a reason. Even if you don't like the reason, there is still a reason. And if someone wants to leave, then forcing them to come back doesn't take away the reason they want to leave.
Focus on you and your children. If your ex decides he wants to work it out, then you'll be a stronger better partner to him.