How to build a curbless shower pan
To long for a comment 
My niece is disabled and uses a wheelchair no curb shower pans are easy but remember the pan is now going to be 2-4x the size of a normal shower. We used a glass brick wall on the center to divide the bathroom up because the large unusual size. For her shower the floor has a slope from the opposing wall all the way back to the drain. We considered a speed bump (very slight) to contain the water that may splash but at 7’ felt it would not be needed. 10 years later the shower is still fully functional. One thing my sister insisted on was thermostatic water valves so if she bumped the valve they would not get froze or burned. The valve has required replacement 1 time recently. The rest of the bathroom floor was raised 3/4 or 1 inch I do not remember. For the floor tiles a rough finished natural stone was used so it would not be slippery when it was sealed, my sister says this is both a blessing and a curse it is not slippery but is hard to clean, we added another outlet close to the opening that she can turn on and spray down the floor pushing the water and soap back to the drain. Since it has a minimal slope. Since this is for an elderly person you might consider a fold away bench. I installed one of these many years ago for an elderly couple in a standard shower. I don’t know if they ever dropped it down but they told me it was very nice.
So you can go totally curbless but you need the pan to extend beyond the splash zone.