I understand that you want to know if you will improve the picture resolution if you upgrade to the SlingLink Turbo adapters (SL150-100).
Although this upgrade will allow you to improve the communication on your home network, it will not represent any modification to the remote video quality.
The most important aspect to take into account on this specific situation is the connection speed you get on both ends (at the Slingbox location and the remote network where your son is). Since you say that you have a good connection speed at your location, I recommend you to ask your son to test the connection from a different remote network.
This test will allow you to determine if the issue is the connection speed at his current remote location. Besides, since you have posted this question under the SlingPlayer for Mobile devices community, I also recommend you to check this link.