We had one of the stretchers for our youngest but it was a pain
to get the legs on and she kept rolling/tipping out of it so we got the girls both blow up mattress when we had the tent.
We then got them all their own swags which is much easier, bit bulkier but can fit two in the CT for overnighters/weekends when our eldest doesn't come and for longer trips they all fit in the bag we had made for the top of the CT.
The swags are great for sleepovers at home too!!!
But not a choice for everyone, especially if room is tight. But by the time we got sleeping bags, mattresses, inflator, etc it's not much more room really. They also will have them for the rest of their lives too.