How can anyone say "how" safe it is? You want statistics? Some say, as
with any other method of transportation, if you get to your destination,
it was safe; if you crash before you get there, it wasn't.

Your concern, having small children, is one shared by many spouses and
SOs, flying and non-flying alike.

Just a couple of *opinions*:
(1) in order to stay on top of all there is to remember and to keep your
actual flying skills sharp, you need to fly regularly, no long lay-offs
between flights. Flying only enough necessary to rent without doing a
checkout beforehand (*generally* once every 60 days -- that varies from
FBO to FBO, depending on the airplane, etc.) is thought by many to be
less safe than flying *more* regularly. If he's working on his
instrument rating, he is not only actively making an effort to increase
his skills/knowledge in order to be as safe as possible, but he's
probably flying often to maintain and build on his skills and is likely
having regular input/evaluation by a CFI;
(2) I'm not so sure about saving money (though having the instrument
rating is a plus with insurance), but being part or full owner of an
airplane means that he would be fully aware of and in a position to
arrange for *maintenance* himself by a mechanic that he knows/trusts ...
as opposed to renting, where some maintenance issues may or may not be
brought to the attention of the facility, may or may not be divulged to
renters, may or may not be addressed in a timely manner, to the degree
YOU would if it were your personal airplane, or by a person whose work
you would put your faith in, etc.

As for there being a small plane crash every time you turn on the news,
airplane crashes are newsworthy and rarely go unreported. Are you
concerned about his safety when he drives to work every morning? ...of
course you are, but my point is, how many automobile crashes are there
every day that never make the news? Most pilots at least *think* about
the possibility each time they fly; do you think about that possibility
every time you load the little ones into the car on a leisurely Sunday
afternoon? Not meaning to make light of your very justifiable concern,
just trying to present a little perspective.