I'll cut to the chase:
Island: Hawaiʻi aka the big island. Trip as a whole will be constrained to here.
Group composition: Groups of 5: Two parents aged 47(F) and 44(M)w/ sons 23(that's me!) & 19 respectively + 5 yr old from much much later. Father is powered wheelchair-bound.
Timeline: Two weeks starting next weekend.
Budget: collectively the group has $20000 to splurge on things outside of housing and sustenance.