Maybe I can make this a little easier for you.
UNLESS your husband need to take large or unusual medical devices, let suggest your give your husband the following challenge:
Make a stack of clothes, etc. and pick any week this spring/early summer and give him the challenge of wearing JUST those clothes for a week for routine activities (other than anything to do with his job, special occasions, sports, mowing the lawn, etc.) I think he'll be able to do it.
At home, he likely wears the same pants/shirts for more than a day. Likely there is somewhere mid-way in your vacation where you will be able to do or have laundry done.
Shoes are always challenging, especially since men's shoes are so much larger. But, stuff items in the shoes and suggest he wear the larger/heavier pair on the plane.
If he is not up for that challenge, then give him the challenge of packing a large piece of luggage (borrow one from a friend), and at last three times each day, have him lift it up over his shoulders 3 times a day and carry up/down a set of stairs, and on other days, have him put it in/out of the car.
In fact, if you want to make it even more realistic, have him make a separate stack of clothes that would be what he would put in the larger suitcase and have him wear those for a week (again, excluding for work, sports, special occasions, mowing the lawn, etc.) and see what items are left over and not used.
But, we find that it is nice to not have to wait to recollect our luggage when going thru customs (because carry-on is already with us), even though we are Global Entry, which does not matter if going thru customs in other countries. And, if something happens where a flight is delayed/cancelled, etc., you will have soooo much more flexibility if you don't have checked bags. We checked a bag returning from Asia recently, because we had a bottle of liquor in it that we were bringing back...........ugh.....how I regretted that....the wait for the bags to then go thru customs......we would have whizzed right thru otherwise. And, remember, you will likely be extra tired and a bit jet lagged when making those connections.
Another time, an airline agent offered us a better routing on the spot, when she learned we were spending an extra night in Atlanta, just because we were trying to head off problems with an upcoming snow/ice storm. She asked if we had checked a bag, we told her no and just pointed to our carry ons, and she said "oh you will be easy" and the next thing we knew we had a flight directly to Barcelona without the throw-away extra night en route to Atlanta. Traveling carry-on can bring some HUGE benefits that you might never anticipate.
Not knowing where you live, you could do a dress rehearsal with city buses or the subway, having him take the larger bag and get on/off a few times during rush hour. Finding a place to put the bag (where he can keep an eye on it and easily access it for quick disembarking).
There are sometimes a few pieces of clothing (a t-shirt or two) in my carry-on bag that I wind up not using on a trip, and I really pack efficiently, but I guess you could say I over packed ....LOL.
Good luck....once he becomes a believer, there is no going back..............
My sister and her husband always check luggage, and for an African safari they took a couple of years ago, her bag arrived at their home (never made it to their destinations in Africa), something like 18 days after she returned home. She said that on the trip, her fellow tour members kindly/jokingly referred to her as "the lady in THE white shirt." So, it is amazing just how little she made it thru that trip with, and likely she would have had more if she had a modest carry-on instead of her checked bag.
Have a wonderful trip.