I have my standard (not cheap) smallish suitcase which does me for most of my world travels. I once purchased a very big suitcase at discount store (cost $20) - put my suitcase INSIDE this and then packed the extra stuff around it. Once I got where I was going I disposed of the large one (I was going to put in rubbish, but one of the hotel staff asked if they could have it).

Bit excessive maybe, but depends what you have to carry.

I always bring a big suitcase (although if you don't watch it, a 28-incher can exceed the total dimension limit if it is an expandable one and you stuff it to the gills). The main problem with that is that you then have to figure out what to do with the suitcase until you come back from Japan. I use a combination of takuhaibin and leaving it with family. I never travel around in Japan with the big suitcase. (I use a backpack plus sometimes a folding duffle bag.)

Another thing I recommend is to use a large corrugated cardboard box (or multiple cardboard boxes) inside the suitcase. This keeps the omiyage nice-looking during transit (a smashed box of chocolate or a package of whole nuts that has been rendered into fragments is not a nice gift). The same box is invaluable for lugging things back. I bring back all kinds of rice crackers and other fragile food items, and they hardly ever break. This is simply not possible if you use conventional cloth or vinyl packing cubes or plastic bags to compartmentalize the stuff. Airlines are ruthless. The cardboard box trick may seem fussy or excessive, but I have done it many times and it is one of the best packing discoveries I have ever made. I use one big box that is as large as the suitcase will hold, and then nest others inside it. Outside of the big box I usually put some of my clothes and other items I use while traveling. When I collect my suitcase at Narita I sometimes take a few items I need out and then send the suitcase to the family via takuhaibin. (Not sure if this will work in your case. Be sure to warn them in advance at any rate.)

Omiyage for five families is a lot! You are wise to start thinking about this in advance and have a plan. I always spend a ridiculous amount of time preplanning luggage logistics, but as a result my trips go smoothly.

You may end up having to put some of the heavier omiyage in your carry-on bag. But be aware that since many airlines have been cutting down on how many pieces of luggage you can check for free (now often none, or 1 piece on international flights), people have been stretching the carry-on allowances to the limits and it can be hard to find overhead bin space for your carry on! If it won't fit under your seat, don't put anything breakable in it, in case you are forced to gate-check it. Gate-checked luggage is sometimes handled VERY violently.

If you and your luggage survive the flight, have a great trip!