Oh can I relate to all of this as well. I am a Type-A neat freak. Or I was until eight years ago. My husband tries to do the housework, and in fact tells me not to because he knows it'll knock me out, but the house is never anywhere near as clean as I would like it. You just have to accept it because the alternative is detrimental to your health.
I don't have kids, so I admit I have no experience with such things, but it seems to me that if you have two teenagers, they should be doing a heck of a lot around the house (including the lawn) even if you AREN'T sick!! Is there any way you and your husband can agree to tell the kids that they need to contribute to the family by taking on chores, and hold them to it?
As for getting your family to understand, I don't know what to suggest, as I've had a hard time getting my own family to understand my limitations, since when I'm being careful, I *seem* fine. With my recent diagnosis I sent out an email to everyone with an explanation of MCAS, a link to the symptoms page on the Canadian Mastocytosis Society's site,
http://www.mastocytosis.ca/signs.htm and an idea of all the weird things that trigger me. I hope they have some better understanding of what all I'm dealing with. If you've ended up in the ER and they're hovering over you worried about you crashing, then they clearly get how dangerous it is for you to overdo it. I guess whenever they hover, you could turn to them and say, "oh, thank you so much for helping out and doing this, since you know I really shouldn't". Take their admission that you shouldn't do it as volunteering to do it themselves.
As for getting time alone, can you all agree on something that will give them peace of mind but give you space? Can you do something like promise that you'll keep a cell phone or cordless phone on your person and speed dial a family member (even if they're in the next room) if you feel you're having difficulty? They worry because they care, and they need reassurance that you won't do anything risky. The lawn mowing doesn't reassure them.
But ultimately I agree with Kim....you just have to let some things go. Just ignore the dust bunnies, the lawn, the dishes, the laundry. If the other family members really need them dealt with, let them deal with them. Your health, not the chores, needs to be your priority. I tend to portion out my energy for the day at the beginning of the day. "I'd like to get the dishwasher unloaded, but if it doesn't happen so be it. If I still have energy, the next thing would be to water the plants in the living room...." That way I have a priority list, and I've learned to stop before I wear myself out. Most important, and it's taken me awhile, I've learned to not beat myself up if some or all of the things are left undone.
There are plenty of us here who do understand...