...The E was almost as large as the D so no reason why there wouldn't be children aboard.
In terms of volume, the Sovereign class Enterprise-E is roughly 40% the size of the Galaxy class Enterprise-D (ray-tracing programs used to calculate volumes on multiple Galaxy and Sovereign models for Trek mods; Galaxy consistently comes in at ~5.2 million m^3, Sovereign at ~2.0 million m^3).
Source (link).
Not "canon" but based on CG models based on official materials, so make of that what you will.
This is another reasons I assumed there were no families onboard the Enterprise-E and why I consider the Sovereign class a replacement for another class of ship (Such as the Excelsior) rather than a direct replacement for the Galaxy class.
Although the Sovereign class is the longest ship in starfleet (mainly due to the length of the nacells) it's probably the 4th largest in stafleet behind the Galaxy, Ambassador and Nebula.
Like I said in a previous post, although more advanced at launch, Picard and Riker might have considered the Enterprise-E and mission profile as a bit of a downgrade.