Hi, we're going to a 4th birthday party of two little boys (DD's school friends) who we don't know and are stuck with ideas for presents. I don't have boys myself, what is 'cool' in the eyes of a 4-year old today? Could buy something 'useful' but would like that 'really happy face' when they open the presents. Don't want to buy toy guns or anything like that (which make my 4-year old godson very happy) either as we don't know how against the parents would be. Any advice?