i think what you need are
'union y' 3/8th", D20820700
and 2x hand valve'union' D20GR0600
so you connect gas to regulator, then connect regulator to union y, which splits it in 2, then run two short runs of 3/8 (say 1foot) then put a hand cut valve on both of them -no more connectors required - these are all push fittings.
you now have gas to two cornies which can be turned off when not in use.
as regards the 'out' side, i presume you want to keep these beers in seperate lines - didnt quite follow you about the counter filler <!-- s:oops: --><img src="{SMILIES_PATH}/icon_redface.gif" alt="

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the cut off valves were about 6 euro, id imagine the splitter is slightly cheaper.
happy hunting!
James