Hi sunnyslope76,
The first place I would start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice for your son … and perhaps more importantly know how and why to avoid the worst ones.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists (based on all the parts of your personal value equation that are most important to you).
The tutorial post also includes several links to lists of the better online options I’m aware of (in the optional online step) that include a wide range of different types of mattresses in a very wide range of budgets as well.
If you let me know your city or zip code I’d also be happy to let you know about any of the better local options or possibilities I’m aware of in your area.
I’m looking forward to finding out what you end up deciding … and of course any comments or more specific questions you may have along the way that I can help with.
Phoenix