Specifically, you might be wondering which important materials are most often forgotten. You have the materials list so I won't duplicate it here but I understand how it feels to show up without something only to realize that particular items was essential.
First, make sure to bring multiple canvases. ( It is useful to tone them in advance with thin grey paint or gesso if you have time)
Second, whether you decide to go with the old master limited palette or the contemporary realist method, it's important to make sure you have your walnut oil AND flake white paint (or lead white, or "lead white replacement") in addition to your titanium white. This particular white paint has a unique quality that will allow for a better weekend painting experience when used in the method we'll discuss.