I went in October of 2003 with my DGF. We really enjoyed it. I am not sure a 4yo would like it or not. It's in a lovely little room, almost like an enclosed porch which is decorated very nicely with Victorian accents. It's very pretty and very refined. I don't recall seeing any children there, but please don't let that discourage you. I am almost positive they had a "kid's menu". If you think it is something she will enjoy, I am sure she will treasure the memories of her "Tea with Mommy" for years. BTW, they had great mimosas!
Having reread this post (I'm the son of a gammar teacher), I would suggest getting ino from allearsnet.com and then going. Know what to expect, but sharing time with your daughter in such a memorable setting is an opportunity not to be missed. Be sure to take a few photos for her to have when she's older, too!