If you are leaving from LAX i would recommend united as there is great availbility in first class. Alos you might consider hilton waikoloa village, its great for families and near half the price on weeklong stays.
There for I would recomend the citi visa hilton card since you can get it over and over. and the hilton amex card, I would wait at least a month after the saphire prior to getting the united card