Here’s the deal. The trundle at Riverside is small. It just is small! If your smallest person doesn’t have a problem with that, then you will be fine.
A great suggestion was made to us many years ago, and we have follwed it ever since. We ship ourselves an Aerobed each and every trip! The shipping is about $11, and we send it to ourselves, to arrive a few days before we do, with the notation “Hold for guest arrival” on the bottom corner of the box. Bell services holds it just fine. On the last day of the trip, we take the package back to te front desk and ship it back to ourselves, which somehow always manages to cost only half as much. Go figure.
Your fifth person will be MUCH more comfortable on a single-sized Aerobed, and it can be stowed away easily each day.
(For us, the issue of five on one bathroom would be a bigger deal than the small rollout bed.)