• You don't need a sheet. Most play yard mattresses, which are thin, can be cleaned, and the bassinet is safer without this extra piece of material, in which a baby could become entrapped. But if you do use one, make sure it is tight-fitting and specifically made for the mattress or bassinet insert on your model. Never use a sheet made for a crib mattress or twin or other size bed.
We purchased 4 sets of these to setup an outdoor play pen for our 1 1/2 year old triplets. Makes for a reasonably sized play area, and so far they haven't though to really try to scale them. Not really many places they could grab a foot hold which is nice. I love the flexibility of how they attach, makes it easy to arrange the space however you want. Very lightweight too, which makes for easy moving when we have the lawn mowed. Can just drag it out of the way.
Some models provide storage for toys and other baby items in zippered side pockets, fabric shelves, hook-on fabric storage pouches, and small clip-on parent-organizer bags. Of course those features aren't necessary, but if you want to use them, look for storage that is big enough to actually hold something. Storage compartments should attach, or be built into the outside of the play yard, so they're out of your baby's reach. One deluxe example is the S1 by Safety 1st Satellite Premier Playard - Pegasus (about $128), which comes with attached shelves and a small laundry hamper.
As much as I wanted to, it’s impossible to keep your eyes on your toddler 24/7. It is not even possible to take a shower peacefully or make a delicious dinner, for that matter, it is not possible to do any other daily chores when your toddler is crawling every corner of your house. That is why many people today are finding this playpen as a better solution to keep your toddler safe and also to do their chores peacefully.
It's helped us out tremendously. It provides a way for us to cordon off a safe space for our son while allowing him an area to freely move. The fact that it breaks apart and can be arranged in various patterns allowed us to expand that space with some creative use of furniture. Sadly though like all young raptors, he's testing the gates, looking for weaknesses that he'll eventually use to escape and terrorize the local populace of cats.