Best Disneyland tips for two elderly parent in WCs

[Judy from Boise]

Our December trip is quickly approaching! Both dad 87.5 and mom 83, will be in WCs I plan to rent and have them delivered to GC. As a nurse I feel strongly that I want to upgrade to adjustable legs to increase comfort, so any company that has rented those to you in good shape would be great to know. things are in a state of flux, but at this point I assume genie + will not have started.
so please give me all of your best tips! I am especially interested in how to best view parades and fireworks without a long wait.
TIA !
judy