t-shirt with a very satisfying result and now I have made this set with t-shirt and shorts for my 8-year old son. With a lot of patience and trials I think I've made the best possible and I've proven that it's actually possble to sew in jersey. Now I just hope he won't find the pattern too childish :)
I don't have any fabrics at home for making clothes from scratch, so when I was in Sweden resently I bought some. In this case the fabrics are from the swedish web-shop znok, the patterns for both t-shirt and shorts (shortend) are from Ottobre 3/2013 and they are sewn in size 140.
Update: Size-wise it's on the limit and the set is an obvious pyjamas according to my son. To me three pockets seems to be overkill on a PJs though... Lesson learnt: use less childish prints for 8-year olds!