Hi Danielle -- Have you started chemo yet? Or done it in the past? Just curious- because I completed chemo a year ago, and was able (physically) to go to WDW after my 5th month (with one month to go)....actually - As my military husband had to relocate without me, I took my 3 yo to WDW by myself for a long weekend - mostly because I NEEDED to find my happy place and just couldn't face my last month of chemo without it (DIsney IS a drug!).
I wore a ballcap with a pin that said "Chemo sucks" - and took it slowly.....I don't think most people even noticed my total lack of hair,,,,and I don't think the castmembers noticed either - they see everything there! You probably won't be able to go commando at the parks - but if you get there when they open (and it's still reasonably cool) and then leave around noon/one for a nap or swim and then head back later then you should be fine (I just kept to the 3 yo's pace!).
I asked about current /previous chemo experience - because you don't want to convince yourself about your capabilites (or lack of) before you even start! Never sell yourself short!! Everyone responds differently to chemo - some get sick, other's don't (I won't even go there...); some lose their hair, others don't ...Some get really tired, other's don't.........Try to keep a positive attitude, and see how you feel . Also, there are many different treatment regimens, and you will have times when you feel better than other's during your cycle (I did Cysplatin /gemzar in a 3 weeks on, 1 week off regimen --- I went to WDW right before the start of my last treatment). I had to have white and red blood cell booster shots at points during chemo, as well as a platelet transfusion - and those things do help.....pester your MD's about your blood counts, and if they get low - ask for the booster shots (procrit was one, I can't think of the name of the other (chemo-brain is my excuse

)...Obviously - if you've already started, or done this before then I am preaching to the choir and just ignore me

.
One more thing to think about - if your counts are low (esp. white blood cells) - you may be more susceptible to infection - and lord knows that WDW is a great place to catch a cold (or other yucky bugs) what with the thousands and thousands of people....talk to your Oncologist! You don't want to end up in the hospital because you caught a cold that your body couldn't fight because of an impaired immune system......
I can't help you with Disney "accomodating" you - because I never inquired (I was a little tired, but with plenty of water, using fastpasses to limit line-waiting and taking rests & swims - I did okay). Disney does publish Handicapped guides that you can pick up at guest relations ----
Wishing you the best of luck !! Jill