If one does the chumrah of turning on the electric lights (and then lights the candles) with the mindset that they should both count as neiros shabbos and makes a bracha on both of them, can someone change a baby’s diaper under those electric light, not in view of the candles?
My understanding of your question is that the lights that the person lit are not in front of the Shabbos candles, rather somewhere else, (otherwise you are changing the baby’s diaper in front of the Shabbos candles). If the lights are not in the place that the actual Shabbos candles are it is permitted. The reason being that this minhag will apply only to the main Shabbos candles, and not to the lights that are lit in other places.
Rema O:CH 275-12.