Jerry, thank you for your very prompt reply! However, it leaves me with a serious question: You state “your wife and child couldn't get benefits on your record while your benefits are suspended”. Perhaps I don’t understand some nuance in your phrasing here, but this would seem to directly contradict the very premise of Larry & Paul’s book, which describes in the first few pages the genesis of the book in a conversation about the benefits of filing, suspending, and collecting spousal benefits. Is the point that, in the case of spousal child-in-care benefits and disabled adult child benefits, these two categories of benefits are only available once a worker has filed for retirement?
Given that my son has already been qualified for SSI benefits due to his disability, may we assume that his qualification for Disabled Adult Child benefits would follow? If they do, the amount he would receive from that benefit would exceed his SSI benefit by about $9000/year. Given the extreme restrictiveness of SSI benefits, it seems we should just stop the SSI benefit and take the Disabled Adult Child benefit since, as you say, the one reduces the other dollar for dollar. However, when I reach 70 and retire, the sum of my benefit and my wife’s benefit would exceed the family maximum, so it would seem that beginning in that year it would be better to drop the Disabled Adult Child and take the SSI disability benefit, since it would add to the total family benefit. But then he would want to resume the Disabled Adult Child Benefit when I die (and the total of my wife’s Widow benefit and his Disabled Adult Child benefit fall below the family maximum). However this presumes that one may suspend both SSI and Disabled Adult Child benefits and maybe that isn’t true?
The first edition of Larry's book was published prior the 2015 Social Security amendments in which Congress largely wiped out the benefits of filing and suspending benefits after April 29 2016(https://www.ssa.gov/planners/retire/suspendfaq.html). You'll want to be sure to read the revised edition of the book released in 2016 (http://www.getwhatsyours.org/laurence-kotlikoff/).
Since your son has been approved for SSI (Supplemental Security Income) benefits, it's very likely that he'd meet the medical requirements for disabled adult child's benefits unless he became disabled after age 22 or if he had substantial earnings after starting on SSI. SSI is a needs based program intended as a last resort source of subsistence level income. A person cannot choose to refuse Social Security benefits in order to receive SSI instead (https://www.ssa.gov/OP_Home/handbook/handbook.21/handbook-2117.html).
The maximization software available on this website is fully updated to handle the 2015 amendments, and is programmed to handle family maximum considerations. You should strongly consider using it to do your Social Security planning.