I've done it both ways on the It's A Small World ride. Both climbing into the regular boat, and using the wheelchair boat. If your family member is using a power chair, and not a
scooter. You can take the power chair on the wheelchair boat. My best friend does that with her power chair when she goes to Disney World as she can't get out of her wheelchair without assistance. Her mom can't lift her in or out either without struggling. I find it easier to roll onto the boat in my manual wheelchair than having to climb down into the boat.