You can make a very inexpensive gathered end hammock from tyvek. The large rolls are 9' tall which, would certainly be long enough for a 5,year old. Gathering the ends and whipping is difficult because the material is very slippery but if you give the ends a light spray of adhesive before you gather/whip, it's very easy. I still bring my Tyvek hammock on canoe camping trips to use as a gear hammock.