I don't know your 6 yo, but we've waited to take kids until they were at least 10. The tour is fun, but long, with lots of walking (through large crowds if the date is closer to the holidays), and the holiday trivia (e.g. origin of Christmas traditions, carols, etc.) may well not interest her. The treats we got were pumpking and chocolate fudge, hot chocolate, gingerbread cookie. You can let the CM know ahead about the no-dairy issue and something else will be provided. But I'm not sure that several hours of walking and trying to listen to a tour guide through a headset will keep your child amused. And HMH was a big part of our tour -- the wait was long and we spent a long time talking about the overlay. You could skip that ride and just wait outside for the rest of the group, but that may not be fun for her or you.
If you plan ahead, it shouldn't be too hard to get a good spot for the parade. That might work better and be a lot less expensive. Just some thoughts. Hope this helps.