1) I'm not sure if another family member can use a vacation home without the deed in their inventory. You need to make sure that one member of the traveling group has the deed to the house in their inventory, even if it's not the Sim that bought the property. If you have bought a vacation home, the game will give you the option of living at base camp or your vac home when the group first lands in the foreign location. If you pick your vac home then all members of the group will go and live there.
2) Vacation home deeds act the same way as any other inventory item when a Sim dies: they are automatically transferred to the next oldest Sim. If you want a particular Sim to "inherit" the deed then just transfer it into their inventory. Last time I played with a vac home was before LN and you had to click on the deed in the Sim's inventory and select an option to transfer the deed to another Sim, it wasn't just grab and drag.
Hope this helps. None of my Sims have had a vacation home since before Ambitions so some of this could have, and probably has, changed. Unchanged: Deeds are transferable between Sims and the whole group will live there while on vacation.
