I think you mean Lily and Bruce? Because Lily and Oscar really don't have any scenes like that.
I'd say it's pretty mild. Sure, there are a bunch of innuendo, but I'm not sure a small-ish kid would even pick those up. But there is a lot of cleavage going on.
Overall I just think the show just wouldn't be very appealing to a kid, more that it being inappropriate?
We took our kids to see this show they are 10 and 7. They have both grown up in the theatre world but there wasn't anything in the show that had questions about,etc. They found it very entertaining and fun esp w/ the tap number. Hope that helps!