The Hilton Amex has no annual fee, so that is a possibility. I'd make sure to get a sign up bonus. How much is your planned HH spend? That's going to be a key piece to deciding on the extra card. I also use the HH Amex for groceries, gas, and Internet. The six points/$ really add up. I put my lower value of HH points at half a cent per point, but usually use them at closer to $.007 to $.01 per point. Those redemption values happen at the two ends of the spectrum.... Cat 2 Hamptons and places like the Tokyo Conrad.

As far as a second airline card... it really depends on how you use it. My In-laws did well by the US card's companion ticket... But if I was going to pay ~ $200 in fees I'd prefer to pay $400 for a single card with lounge access. Otherwise, I'd probably stick with a single *a card...unless you are chasing he sign up bonus.