I use an old 10 speed crankset with 12 speed FD, RD, chain, and cassette. I have not dropped the chain nor has it fell between the two rings.
If your crankset does not work with the components selected, you'll know pretty quickly. I would try it. IIRC, 9 speed rings are a little thicker and spaced a little further apart than 10 speed setups.
Nobody knows the OP and whether 50/34 is too much. She has already said she was going with light gear, 10-15 pounds IIRC. It is not hard to get total bike and gear weight under 40 pounds but 30 pounds is a challenge. In that weight range, such gearing as she listed is not extreme for a moderately fit cyclists.