My DD10 also has moderate bilateral loss and wears bilateral aids. Her hearing loss wasn't detected until KINDERGARTEN! She has been going to WDW since she was 9 mos old (we have 4 kids, 10-20 years old, if we waited for her to be "old enough" the oldest would have been "too old"!)....
....in kindergarten we tried the t-coil head phone thingies (okay, not exact verbage). The problem was that it made EVERYTHING too loud- including the loud scary sounds (think about the dinosaurs on Ellen!). We selectively used them once we realized it scared the holy bejabbers out of her....quiet rides/shows- yes. Louder rides- no way.
Last summer we tried the handhelds, as she is a good reader now. She didn't like the disconnect between the screen words and the sound. She LOVES the reflective captioning- in fact, at Mickey's Philharmagic she discovered that Donald SAYS WORDS! (she never realized either he or Mickey said real words before- thought it was just "animal noise")!
My best advice is 1) listen and consult Talking Hands- she is the resident expert; and 2) try different things and see what works for you. Be sure and ask for front row seating, if that helps (you can get a GAC for that- no avoiding the lines, of course, but it really can help).
We also make small "business cards" that say "L is hard of hearing, please look at her when speaking. Thank you so very much!"....we show them to the face (talking) characters quietly and slyly- no embarrassing DD and the characters have been SO nice about crouching down and talking to her face to face. We haven't run into a bad character yet when doing this! (well, Captain Hook is still "bad" and Tigger is still trouble!).
It will get easier as your DS gets older and reads more fluently. Good luck....and I don't know if you know about the ListenUp! website for parents of children who are deaf/hard of hearing. Has lots of great ideas and information.
http://members.tripod.com/listenup/toc.htm. Second best site next to the DIS!