Babies, UMs and the handicapped can't sit in exit rows--they don't qualify to help in an emergency. The agent was confusing them with bulkheads.

I book exit row seats all the time, domestically and internationally. I've never had them taken away. Don't worry.

If you're inclined to worry, do online checkin at 24 hours ahead. If your seats are still intact, you'll have boarding passes in hand. If they've disappeared, you'll have the best choice of remaining seats (and the most time to raise a fuss with NWA).

If it's a KL-operated flight, though, all bets are off. In that case, the seat assignment really is a request, and much more likely to go astray.