I found this article on Parent24.com as a blog repsonse. Although written by a dad, read this as a parent and think again when you say "in the best interest of my child":
"The legal and moral reality is that both of you have full parental responsibilities and rights in respect of your child. In simple terms this means you both have the identical rights (and responsibilities) to co-parent your child. Mothers are not better or more appropriate parents than fathers - please come to terms with this.
There is no "appropriate age" for sleepovers and you certainly don't have any basis in fact of law to control your child and prevent him having lawful contact with his biological father. Historically, "maternally preference rule" biased "experts" often quote "child's best interest" when trying to control (limit) the child from having lawful contact with his father. "Best interests of the child" used to be a convenient catch all phrase that really meant "mother's best interests" or mothers know best. In doing this these "experts" claim that mothers are somehow better equipped than fathers to co-parent their own children solely by virtue of their gender.
This is nonsense, has no basis in fact of law and no basis in any reputable study, and the Children's Act concurs. The Children's Act now defines "best interests", it's no longer ethereal opinion and no longer catch all phrase! The Act specifically contains no gender prejudice, nor is there any mention of "age appropriate" anything - co-parenting means equal parenting. The persistent "mothers know better" claims are throwbacks to the debunked "maternal preference law". Of course I understand your love and concern for your son. Why do you assume that the father does not have the same love and concern for his child? The fact that you only allow him to see his own child once a month? What makes you special, the preferred parent - your gender? Forgive me if I appear blunt, but it 's high time that mother's realised that although they may no longer love the father of their child, the child still loves his father and is as entitled to be co-parented by his father as his mother it's in his best interest. I'm not suggesting that the following applies in your case, but many mothers continue to exhibit controlling behaviour toward their child and deny or prevent legal contact between the father and the children. The Domestic Violence act describes this controlling behaviour as an act of domestic violence - child abuse to put it simply. I'm sure you truly love your son, as does his father. Spend some time with him and your son and take him through your son's routine - believe me (other than breastfeed) he can do whatever you can do, and your child need a father and a mother. How do I know? Well I single parented new born triplets (my first and only children) while their mother was away with her lover - so it's probably fair to say I speak from some experience."