First, multimember LLC's are required to file a separate tax return for the business entity. You will need to file a 1065 Form for the multimember LLC that was created in 2017 (of which your husband and son were members). The business activity would be from the date it was formed (7/18/17) to the end of the year. (You are correct that Form 1065 is also the income tax form used to file partnership returns.) The LLC tax return will also generate a K-1 form for each member for them to include on their personal tax returns.
TurboTax Business (CD or download) is the product needed to create a multimember LLC tax return (Form 1065). TurboTax Business does not create personal tax returns, so you will have to use TurboTax Self Employed (Online) or TurboTax Home & Business (CD or Download) to create the personal returns. The links provided in the product names include more information about each product. The online products can only file one federal return per login ID, whereas the CD/download products can prepare/generate more than one return. (There may be limits as to how many can be filed electronically, though, but more can be printed and mailed.)
Second, for the two sole proprietor businesses from the first part of the year (1/1 - 7/17/17), you are correct that these would be included in the corresponding Schedule Cs of the personal returns. Your husband's sole proprietor business would be on his (or your joint) return and your son's sole proprietor business would be reported on Schedule C of his return.
Third, if your son has another sole proprietor business (graphic design), then, yes, he would file this information on another Schedule C form with his personal tax return.
[Edited 2/8/18, 3:40 pm]
