Why would you assume this targeted three people? I assume the most likely scenario is that the attackers targeted as many Hezbollah members as they could, and were extremely successful at it.
That's a very good point - if the goal was to disable comms and incapacitate as many targets as possible, then collateral damage numbers are much lower.
It's unknown how many were family members of targeted individuals, and whatever the number actually is, it'll be misreported.
Why would the family members of a Hezbollah operative be carrying a pager tuned to Hezbollah's private communications network? A reminder that Hezbollah operates a parallel phone system, and is in many ways more sophisticated and organized than the de jure government of Lebanon, whose military forces Hezbollah outnumbers.
The family member would not necessarily need to be carrying the pager, just near it. Picture a child standing next to adult, pager on hip would be next to the kids head. Pagers are not always worn too, could be on top of a table, etc..
It's unknown how many were family members of targeted individuals, and whatever the number actually is, it'll be misreported.