Unless all policies lapse at the same time, you may end up paying administration fees on each policy. The alternative is a family policy by the likes of Admiral or Aviva (though I am not a fan of these). The best thing to do is wait for the most expensive premium to lapse first. Have whoever is going to use that vehicle then insure it. And then let the rest follow suit. If your son is over 25, then all of you will have the extension to drive other vehicles third party, which should allow some cross over for you all to use any vehicle while swapping over. You might find if you do them all at one on the same day, you and your wife's premiums may go down, while your sons goes up, it may counterbalance any admin fees.