Laura, this "burden" thing is a self-fulfilling prophecy. The more you feel like a burden, the more likely you will be.
Caregivers [did you see that "giver" part?] don't want or need to hear about their burden (though we appreciate appreciation from time to time). We don't want or need you to have a sad face of regret for what we have chosen freely to do.
Did you ever help someone with mobility challenges reach a shelf, get a door open, pick something up? Did you want to hear about what a burden they were being or did you just want to help and make something better in both your lives? When you have helped someone for a longer period, were you not the better for it?
Your caregivers' and companions' lives [and, unexpectedly, the lives of many others that you will touch] are going to change forever, that is true. The question is, what kind of change do you want to leave them with, when you are no longer here? The regret of having failed to pull you away from a bleak journey to death or the thrill of having helped you live your life to the fullest and most joyful?
Your family and friends want to be with you, help you, have fun in all the ways you still can (and there are a lot!), celebrate the good, regret the less good, and live both the parts of their lives that will change because you are ill in conjunction with -- and this is very important -- the parts that do not, the people, places, memories and history they and you still are. If you deprive them of that, you'll all regret it. There is always a sunbeam to sit in (especially where you are!)
In sunshine [though Seattle today is not],
Laurie