Yes, we used it last year when she was under 2. According to local lore, SAS will refuse a 2 y/o on *A flights (you get +4 if flying SAS, though), but maybe ET is more lenient.
On a site note, their minimum bid for upgrade isnt half bad, starting at 355 OSL-ADD and just north of 400 ADD-OSL. Should anyone consider buying lounge access at 90, might as well just shoot for an upgrade instead.