score:4
Singapore Changi has only three Star Alliance lounges: the Singapore Airlines KrisFlyer Gold lounges in T2 and T3, and a Royal Silk Thai Airways lounge in T1. (There are a couple of contract lounges as well, but these are only accessible if you're flying their contracted airlines like United or Air China.) All appear to officially apply the Star Alliance lounge policy, which allows only one (1) guest, excepting only children under two.
However, in practice, anecdotal evidence says that Singapore Airlines does allow children to enter with their families. This proved to be the case for us as well: we were told the official policy, but let in as a "one-time exception" before I even had the chance to ask. It likely helped that the lounge was fairly quiet at the time.