Hello and thank you for your question.
Either parent can bring an application for new custodial access orders if they are concerned about the current arrangements and believe they should be changed, but at eight years of age the child is almost certainly too young to have their preferences given much weight.
The court determines custody/access issues based on what it believes is in the best interests of the child and there is a strong presumption that it is in the best interests of a child for it to maintain and develop a good relationship with both parents and it is only where there is evidence that a parent either poses a danger to the child in some way, because of violence, drugs, criminal or mental issues that a parent would normally be denied access or custody.
In your case the unhappiness of the child may just reflect that his father is not much fun for an eight year old to be with, or it could be a sign of mistreatment by the father, but you won't be able to sensibly take action without a firmer basis than you have at present.
If communication was better with the father it would be wise if someone from the mother's family could discuss such concerns to see whether the problem can be identified, but in the absence of such an option, I would suggest you talk to a doctor, preferrably one familiar with the child, and perhaps have the child referred for assessment by a child psychologist. If they think there is an issue that needs to be addressed then likely an application to the family court could be considered, but I would suggest you consult with a fully briefed family lawyer before you pursue family court action as you will want to be clear exactly what outcome you want to get from any application and will want to ensure all your evidence is properly prepared and justifies such action. Simply applying to the court or alleging abuse or similar to police without the assistance of a family lawyer may not lead to the outcome you want and may in fact backfire if it later appears any allegations were made without a proper basis.
I trust the above assists.
Good luck and PLEASE RATE MY ANSWER.