1) Shower Curtains
2) Brooding Light (bulbs, hood, thermometer)
3) 1 Gallon Waterer and Feeder trough
4) Medicated Chick Starter Feed
5) Sugar or Sav-A-Chick packs for their first few days.
6) Flake PINE shavings
1) I'd line the pack and play in something that can be cleaned easily. Perhaps a shower curtain. Get 2 so that you can hose and dry one after doing complete litter changes but still be ready to get the babies back in their playpen as soon as possible.
2) The chicks have to be kept at certain temperatures so brooding light bulbs at different wattages, the hood to direct the heat, and a thermometer to dry run it to make sure the temps are OK.
3) Self Explanatory, won't need a full gallon, but I find they are least likely to tip over
4) I prefer medicated to prevent the onset of coccidia which is common in chicks, however that is your call. You do want Chick Starter feed, it is usually pretty clearly labled on the bag, however be aware that you do not get the stuff for broiler chickens (cornish rock/meat chickens) if you are getting layers.
5) Many people recommend sugar water or save a chick water (we call it Chicken Kool-Aid at my house) as it helps the chicks get over the stress from the trip to your home.
6) The larger cut the shaving, the better as chicks may ingest the really fine stuff. Also, DO NOT USE CEDAR! as it is poisonous to them.
Anyway, that's what I'd start with. I'd also recommend to start thinking about some kind of something to put on top of the Pack N Play to keep them from flying out.
Grats on your babies!