Sound attenuation for noise transfer starts way before the flooring selection. Flooring pads do not do a lot to cut down on noise transmission. This is why carpets are often chosen for bedrooms. It doesn't stop noise, if the home wasn't built to stop noise. But it absorbs it.

Will the flooring be glued, nailed or floated?

Do whatever you can.

They were planning to glue the floors, but if we put a soundproofing barrier, they would be floated

I would want the floors nailed, and put some thicker area rugs in the areas where the kids run or play.

Glue hardwood on a second story? Is that normal in some places? In my world, hardwood floors are nailed. If they aren't nailed, they aren't hardwoods.

Floating is something you typically do with laminate or vinyl.

Can you give a better description of the floors? Thickness? Engineered?

Foot impact noise is really hard to deal with. Concrete floors like in a high rise is probably the best way. Other than that - kids should sleep in their room but play somewhere else - IMO.

They are engineered hardwood 3/8” thickness

Depending on the state of your house (is this a new build?) you can put additional mass underneath the subfloor (like drywall), add insulation between the floors, and add mass to your ceiling drywall. See https://www.soundproofingcompany.com/soundproofing-solutions/soundproofing-ceilings for some ideas.

Interesting, I do not see ideas, I see an ad for a soundproofing company.

thefitzs02 , also keep in mind some adhesives include sound deadening properties. Make sure you look at that as option as well.

"Interesting, I do not see ideas, I see an ad for a soundproofing company."

You should look more closely then. Jeez, it's no wonder it's the same 10 people that are active here, as they chase everyone else away who's trying to help.

Yes, it's a company that sells products, but they have a lot of info there, such as:

1) screwing/gluing drywall to the subfloor, between the ceiling joists

2) adding mass via the ceiling drywall (using 5/8" instead of 1/2", and/or doubling-up)

3) mechanically isolating the drywall from the ceiling joists

It's a lot more helpful to point people at pictures and articles/research (with actual tested STC values), no? I've missed your helpful contributions on this topic...

Since you're gluing there will be no mechanical fasteners to transmit sound to the structure below. This allows you to use a standard sound deadening product like cork, rubber or composite sheet like WhisperMat, SuperSam, Proflex 90, or the like. The makers of the last three products tout superior results, but I'm skeptical. Jason has the right idea. Adding mass between the two will reduce the transfer of airborne sound. That makes a heavier option like rubber ideal for airborne transmission. That probably matters less in a house than in a condo because you already have an opening to the upstairs. To reduce transmission of impact sound you want to isolate the upper wear surface from the subfloor. If your material can be floated, that helps isolation and you can use a less expensive product like QuietWalk, but pay attention to how it would affect sound upstairs. Some floating underlayments result in a tapping sound, like walking on loose tile, especially with hard shoes.

The solutions in Jason's link are excellent. The most common one is LEVEL 2 with a double layer drywall ceiling attached to horizontal metal channels that are attached to the joists with resilient clips. https://www.google.com/search?client=safari&rls=en&q=acoustic+clips&ie=UTF-8&oe=UTF-8

A less expensive but less effective method is to attach the drywall ceiling to the joists with resilient channels. https://www.google.com/search?client=safari&rls=en&q=rci+resilient+channels&ie=UTF-8&oe=UTF-8

Avoid rcessed lighting in the ceiling.

Avoid rcessed lighting in the ceiling

Folks building home theaters often build custom "backer boxes" for recessed lights made of plywood + sheetrock to compensate for the drawbacks of can lights, if one must have them

Hopefully you don't have a 2-story family room and/or foyer open to the second floor ... that would be your biggest source of sound transmission.

It is a remodel so unfortunately I’m not sure about adding mass between the 2 stories

Good luck! Our poor tenants hear us downstairs and I’m sure it’s awful. We totally believed we had done enough but it’s clear we needed to do far more for it to work. I’m so glad we have carpet upstairs in bedrooms and don’t hear the kids when we are on main floor.

Do you have particularly rambunctious children? In my previous home, the second story had nailed oak flooring theoughout with a 1-1/8" tongue-and-groove, plywood subfloor that was glued and screwed to the joists. I never noticed any noise issues.