With the amount of flying you plan, you will be star gold regardless of which star airline(s) you fly and which program you credit your flights. The question for you should probably be which Star program you pick (or whether you should pick oneworld instead). If you and family will be flying a lot of domestic US flights (that are not part of your international P itinerary, then mileage plus may make more sense). If, however, most of your flights are international then you should probably look more at comparative benefits to you of the individual programs (mileage plus still ranks very high for many travelers) and also consider which airline you are likely to use the most (as there will be unique advantages of having top tier on that airline).