hope your grandpa gets better, but realistically, when dealing with family who may or may not be as understanding of hidden city, why risk it, technically you are already going against every T&C of airline rules with hidden city, but 99% of the time, airlines don't make a big deal, an unwritten rule of hidden city tickets is just use carryons. Shipping luggage to your real final destination might be something to take into consideration... lot of luggage, hidden city and elder passengers... no offense, but that a recipe for disaster!
I'm not playing airline defense here, but don't believe that somehow an airline agent will believe that all X amount of bags must be picked up in city XYZ before going to ABC...
if you want to play hidden city games, play by the rules (no carryon, etc)...