Although your sons should be covered, you might want to tell your agent about this arrangement…just in case. There are some parts of the policy that have “grey” information about who is allowed (or not) to drive the car. Because your boys do not live with you, they are not household members, so you don’t have to list them. However, the policy will also exclude anyone who “regularly” uses the car.
“Regularly” is talked about in the policy as opposed to “occasionally.” It sounds to me like “occasional use,” but if your sons use the car at regular intervals, say every three months, you could get an adjuster who defines those regular intervals as “regular use.” Such an adjuster could have grounds to deny your claim for collision damage, rental, towing and any other optional coverage you have on the car.
You are better off letting the underwriting representative or agent know your boys use your car once in a while and let her tell you if you should list them as drivers. Get a follow up letter from the representative that documents the advice given to you. With all this on file, a claims adjuster will be much more trusting and less likely to drag out a claim because of suspicion that you have an unlisted operator driving your car on a regular basis.