Thank you for your email. I apologise for the delay in getting back to you. I hope you don't mind if I respond in English as my Afrikaans is not that good.
I understand how concerned you are about your son. It is very normal for a 3/4 year old to want to sleep with his parents or near his parents. As he is an anxious child I would encourage you to sit with him, gently soothing him until he falls asleep in his room, and then allow him to come to your bed to cuddle in the middle of the night, if you and your husband can sleep with him in your bed, or allow him to lie on the mattress next to your bed. As he gets older and gains more confidence he will begin spending more time alone in his own bed. There are many children who sleep with their parents or come for a cuddle in the middle of the night that are older than your son.Sleeping in the same room as his sister may help him to feel secure.
Try not to be too anxious about him going to school. Most children are not eager to separate from their parents and don't like the idea of being alone at school. However, once they get used to the school environment, their teacher, and make a friend, they find separating easier. Talk to the school and your work, and arrange to stay at school with him until he settles. Also ask the teacher's to help you. An empathic teacher may be able to settle him easily. If he is continuously very distressed and screams, and nothing seems to work with regards to settling him at school, then you may have to keep him at home and try again in 6 months.
Your son appears to be a very sensitive, anxious child, and it is imperative that you try to be calm and in control when dealing with him, as he will be able to sense your anxiety. It is also essential that you are sensitive to his needs and ensure that he is not left alone. Constantly reassure him that you and his father love him very much and will not leave him. He may have had a traumatic experience with a care giver who did not attend to him when he was younger, or this may just be his personality He needs to feel secure and safe to develop self confidence and become more independent. Be conscious of this when dealing with him and allow him to develop at his own pace, without any pressure from you or your husband. Help him to find the words to express how he feels when he is upset or anxious. "You feel very upset when mommy leaves to go to work. It makes you feel alone and sad because you can't be with mom. I understand it's not easy for you. I promise I will be back later." You may also want to consider installing a video camera in your home to see how your son behaves when you are away, and how your caregiver handles him when you are not around. It may give you clues as how to help reassure him.
I am very concerned that such a young child has been diagnosed with ADHD and is on medication. I urge you to take him to a specialist neuro paediatrician, and have him reassesed. I would encourage you not to label him with a disorder when he is still developing his personality and learning new skills. Children tend to live up to the label they are given. Even though medication has helped to subdue him, and in some cases may be essential, you should constantly aim with the help of professionals to find alternative ways of managing your son. Ensure that you keep up to date with research being done on ADHD and the medication he is on.
I can recommend a fabulous book titled Connection Parenting by Pam Leo. You should be able to get it on Kalahari.net
Good luck! Let me know how your little boy is doing.