Need help please

Hi everyone!
I have a wndr3400v2 net gear router. It has the 2.4ghz and the 5g. My iPad and my directv will read the 5g no problem but my daughters laptop and her Xbox will not. I know this is because they are not dual band. My problem is no device in the house will connect to the 2.4ghz unless I turn off the security password and make my connection unsecured. Both the 2.4 and the 5g have the same password. I have tried resetting the router changing the SSID nothing seems to work. I really hate having my Internet not secured so if anyone has any ideas On how I can try to fix this I would be most greatful.

Thanks
Mike