Price for both seems right.
A 14' boat is fine for diving 3 people (and in truth is not large for a SIB); you will be able to take as many as 6, but space is going to go away (I had 7 on my 14' Achilles once. We were able to move, but just barely. Luckily we weren't planning on diving anywhere far away from the ramp, so my daily parking pass worked out.)
Plenty of room for wife and 2 kids, but you will probably have to come up with some more comfortable seating (depending on the age of the kids, I would be hesitant about them sitting on the tubes as is normal in a SIB.)
If the current owner is willing to take a bit of time showing you the boat, I'd do one other test (in addition to what everyone else has suggested): Deflate each chamber to completely slack, then fill every other one in turn, separately. You should be able to get one chamber near-full without the others inflating (they may become a bit more full due to the baffle flopping, but should not come up firm.) If more than one fills, there may be leaking baffles. That would not necessarily be a deal-breaker to me, but it might warrant a bit more haggling on price. And it's something good to know in case you buy it and develop a leak on the water.
I wouldn't necessarily count on the motor starting on the first pull, either.
They rarely do so routinely.