Don't know a solution as desired.
Probably this might do it for you:
1) the pc game or the game launcher already contains an age restriction / parental control.
for example Steam contains a family option
2) create a filter in AM with games less 18 AND set the button for 'Next Display' to a combination of simultane buttons:
goto AM folder > romlists > choose the textfile of your emulator system > enter at the end of your 18 games 18 (this is the column for Rating)
start AM > press TAB key > Displays > choose your emulator system > Add filter > enter a name (like KIDS) > Add rule > Target : Rating > Comparison : does not equal > Filter Value 18
start AM > press TAB key > Controls > Next Filter > Remove Input
start AM > press TAB key > Controls > Previous Filter > Remove Input
start AM > press TAB key > Controls > Next Filter > Add Input > press for example three, four buttons simultane
set all your emulator systems to KIDS filters
every time you exit AM, AM saves last state (which filter was choosen last time). So you need this final step:
goto AM folder > right mouse button on file : attract.am > set write protection
3) create a filter in AM with games less 18 AND remove Input for Next Filter/Previous Filter AND use KONAMI Code Plugin for filters menu
goto AM folder > romlists > choose the textfile of your emulator system > enter at the end of your 18 games 18 (this is the column for Rating)
start AM > press TAB key > Displays > choose your emulator system > Add filter > enter a name (like KIDS) > Add rule > Target : Rating > Comparison : does not equal > Filter Value 18
start AM > press TAB key > Plug-Ins > KonamiCode > Enabled : Yes > Code Sequence : for example : up, up, up, down, down, up > Action : filters_menu > Up control : Up > Down control : Down
start AM > press TAB key > Controls > Next Filter > Remove Input
start AM > press TAB key > Controls > Previous Filter > Remove Input
if you press up, up, up, down, down, up you'll get a menu of filters
set all your emulator systems to KIDS filters
every time you exit AM, AM saves last state (which filter was choosen last time). So you need this final step:
goto AM folder > right mouse button on file : attract.am > set write protection