I've just hit BAEC Silver

and have 2 questions:
Firstly, if I don't retain Silver will I get a soft landing to Bronze (if I haven't made it anyway), or are soft landings only from Gold to Silver?
Secondly, my next flight is from Gatwick and I will have my children and wife with me. I know I can guest my wife into the LGW Terrace Lounge, but do they allow infant-age children in?