How lovely . I have 3 DD although older than yours. My middle DD has always been like your DC. In my experience the only downside is if they aren't willing to include other children their games or get possessive. My DD is fine letting friends in on the game but not too keen on younger DD getting involved, I insist that she lets her play some of the time (especially as DD3 is the opposite and won't play on her own at all!).