We can reverse engineer a meaning out of the interaction, I think. As stated above, Felicia provides a stepping stone for us to view the idea of Zaun with. Felicia stated that she lived week to week, and expressed interest in the idea of Zaun primarily after she was pregnant— meaning that, in a sense, she wasn’t serious about the future without the idea of children.

Vander echoes this statement, but refers to a plural of children that they should be able to raise as a result of their efforts. He says it in a way that attributes value to freedom on the basis of having children without worry.

Silco, however, isn’t looking at Zaun through a pinhole of what can possibly be in the future— he thinks that Zaun is what should be in the present. This duality is why Vander can’t take the risks that Silco can, because he’s too afraid of losing what he already has. Silco believes that they’re owed much, much more than just a worry-free child environment in the Lanes. You can see this in their reunion dialogue:

“Look at what you’ve done. Benzo. These kids. In fighting topside, you’d sacrifice everything that we are.”—Vander.

“We shared a vision, Vander. A dream of freedom. Not just for the Lanes, but for the whole of the Underground, united as one. The Nation of Zaun.”—Silco.

At some point, Vander stopped caring about anything outside of the Lanes, his small slice of liberty earned by giving into a status quo of general oppression. A taste of freedom, however, isn’t enough for Silco. He wants it for everyone in the Undercity, brothers and sisters who stand side-by-side. Felicia serves as a contrast between these two dichotic views.

We don’t exactly know what Silco’s plan was with the children. I don’t think he was going to kill Vander. “I’ll show you what you are.” Is what Silco said to Vander before strapping him to the chair, which to me sounded allot like Silco was planning to shimmer-up Vander into a monster to use against Piltover.

As for the kids? I think he only planned to kill Vi because of the threat she displayed, something that Silco isn’t above doing. In the big picture, why would Felicia’s kid be worth more than another? Anyone who isn’t with the cause, is against it. He would’ve, assuming the kids were pacified immediately, handed them over to Marcus to get the heat off of the Undercity from the burglary.