Low heights are for the bakery areas where you are kneading bread and rolling out dough, but 18" sounds really really low. That's just 1 1/2 feet. Was there a typo?

For the high area, does DH work in the kitchen? Use boxes, etc., to create a space for him to "work" to find what height would be comfortable for him. Decide where that higher space would work best in your kitchen.

We aren't tall - 5'6" and 5'7", but I wanted my counters to be at least 37". They ended up being 37.5" and I like the height. I don't have varying heights but lots of people on this site do.

Don't forget that cabinets are usually installed before flooring, so be sure your kitchen person knows you want a specific height from the installed floor, not from the subfloor.

Another thing to remember/consider is that you can put a nice, thick butcherblock on a counter to raise a work surface for a taller person, but a step or something for a smaller person to use a too-high counter would be a tripping hazard.

I'm about 5'4", my dh and tallest son are under 5'11", with the other kids smaller and in-between our heights. We have the island, baking counter, and stove run at 33 or 34", while the cleanup area and breakfast counter (where toaster oven is) are at 36". With the difference in your heights, you have quite a challenge to meet your needs and those of your dh! I guess I'd want specific areas to each person's best working height, then a compromise with the rest, leaning more toward your needs because of what I pointed ou in the first paragraph. Mocking up the heights and using them for awhile, if possible, will be your best help, I think. Best wishes.

All of our counters are the same height including our island. We went higher than standard...approximately 37 3/4 inches high. I am only 5'4'' and hubby is 6' and we both enjoy the height. It felt funny for about a week, but I quickly adapted and I find my back doesn't hurt nearly as much doing the dishes either.

To find the best work height for each of you, stand straight with your arms at your sides. Now, bend your elbow 90o while keeping that arm at your side and measure the distance b/w your elbow and the floor (you'll need help with the measuring).

This distance will vary, even among people the same height b/c it is not only dependent on your height, but also on your upper arm length.

You and your DH will, of course, have very different "ideal" work heights, so... How often do each of you work in the kitchen?
What do each of you do in the kitchen?
Are there any tasks that one or the other of you does almost exclusively? (E.g., Does one of you do the majority of cleanup? Who does most of the prep work...one of you or is it frequently shared? etc.)

How much countertop space will you have in your kitchen?

How will that space be allocated?

Will there be more than one run of countertop? (Wall runs, island, peninsula, etc.)

Ah, you have the best of both worlds, in that someone can always easily reach the low or the high items! :)

Have you thought about building into your toekick area pullout steps? Haefele also makes a step stool that folds up and can be store in a toekick pullout.

You guys are awesome. Thanks for all of your suggestions. Thank you thank you thank you