Go with SNA unless the price difference is huge. Try to avoid ONT and LAX. 45 minutes away=$80 shuttle ride each way(depending on the size of your family)
I've never been to SNA but I think Long Beach is the best. It is a very small airport but it is never crowded. If you can fly in there I would go for it.
Everyone so far has voted for SNA and I have to agree it seems nicer to do so, BUT we still choose LAX simply because of price. We can find a way cheaper price into LAX from here, but not SNA so the choice is made for us.
Really, it depends on where you are coming from and the price.
If the price is all the same, (or close) for your dates of travel, I would go SNA.
Whenever we vacation I try to find a flight into SNA because that's what many seem to prefer. Still, we've only flown into LAX and ONT. Of the two we prefer ONT.