A death, inherited IRA, unless is spousal transfer, demands immediate required withdrawal. The length and amount of withdrawal can be considered. Your minor son can take it out as minimum distribution over his life time.
Below is a citation from an IRS website. Two links are also attached for your reference.
It seems that this "transfer" you are considering as "roll over" could be considered as "total distribution" by the insurance company.
Please don't do it yet until you are very sure.
What your son should do is to transfer the annuity to a inherited IRA account. Ask the insurance company how it can be done. Then, he is to immediately start to withdraw based on the law. If you would like to keep the tax to the minimum, then, he can withdraw with his expected life time. Because the insurance company is required to withhold tax, you can let them do so with the lowest percentage they are willing to do, say 10%. Then, when you report tax on your son's tax return, say if he gets $600 distribution in a year, it is likely that he would not owe tax, then, the tax withheld will be refunded to him.
Please make sure that the account he is transferring to is titled with his name and specifically titled "INHERITED IRA" account. This is very important. Please continue to read on the citation and links. Feel free to follow up with questions.
Fiona Chen, MPA, Ph.D., CPA, ABV, CFF, CITP
Inherited from someone other than spouse. If the inherited traditional IRA is from anyone other than a deceased spouse, the beneficiary cannot treat it as his or her own. This means that the beneficiary cannot make any contributions to the IRA or roll over any amounts into or out of the inherited IRA. However, the beneficiary can make a trustee-to-trustee transfer as long as the IRA into which amounts are being moved is set up and maintained in the name of the deceased IRA owner for the benefit of the beneficiary.
Like the original owner, the beneficiary generally will not owe tax on the assets in the IRA until he or she receives distributions from it.