Hello Lynn!
Thank you for visiting the Disney Parks Moms Panel. I completely understand the need for transportation options for little ones. Most of my girls loved our double stroller, but there's always one who likes to have a mind of her own.
The official policy on Keenz Stroller Wagons has not changed, and they are still considered wagons and on the list of
prohibited items. There may be instances where your mileage may vary depending on the Cast Member's decision, but if it were me, I'd rather not risk being turned away at the
theme park entrance.
If your sister-in-law does not want to bring her own stroller, there are
Disney Featured Providers that rent strollers that recline and are easy to push. My children always liked the City Mini Single and City Mini Double and often napped in them while the older kids rode the more thrilling attractions.
If you have any other questions, please come back and see us real soon!
Tania