prove to them with documents that you will be coming back to Qatar, this is to eliminate the suspicion that you will be staying beyond the 6-month allowable stay in the US. and just a tip, don't apply at one time. too many family members applying at the same time is not good. though your intention is good to celebrate thanksgiving, chances are you will be rejected. why don't you apply first. try it out. then the rest will apply later on.