1. PLANNING: Have the newbies make a list of their MUST DOs. Then make a list of their WOULD LIKE TO DOs. Plan the day(s) to make sure you hit the MUST DOs, and fill in as many LIKE TOs as you can.
2. SHOES: Bring more than one pair of comfortable shoes, and switch off. (Either during the day, or at least every day.) I brought tennies, Crocs, sandals and flip-flops. I found out the (newish) sandals gave me a couple blisters, so wore the tennies in the a.m., then the Crocs or flip-flops in the evening. If I wore one pair of shoes the whole day (because we didn't return to the hotel until the park closed), then I made sure to start the next day with a different pair of footwear. My feet felt great!
3. SPECIAL EVENTS: Make reservations for character meals, Fantasmic Balcony seats, or other similar events ahead of time. It would be sad to have something on your MUST DO list that you miss because they're all booked up.
4. GO WITH THE FLOW: I know this seems to negate the Plan Ahead philosophy, but if you aren't terribly pressed for time, don't plan everything down to the minute. There are so many little charms about DL that you discover along the way, so it would be nice to be able to go with the flow as time permits. We headed to NOS when DS2 fell asleep in the stroller rather than taking him back to the hotel as we'd planned. We enjoyed the quiet shade there. As it turns out, it's also where the pirate band and Cap'n Jack exit 'off-stage', so we also witnessed a few sweet little guest interactions there as well.
5. SEE THE ALADDIN MUSICAL!: If you can, see this musical! Everyone raves about it. We were unable to see it during our trip because they were re-casting, but it's supposed to be spectacular and enjoyable for everyone!
6. GET 'FIRST TRIP TO DL' BUTTONS: I wish we'd known about these before our first trip last fall. You can pick them up at City Hall, or I believe at an onsite hotel. We got birthday buttons for our kids, and the CMs were so wonderful about calling out to the kids or chatting them up while we waited in line. They loved it!
I agree with everyone else's posts about Fastpasses (and knowing how to maximize their use!), finding a parade or fireworks location, etc.
Their first trip is going to be magical no matter what, so a little insider information just makes it extra special. I hope you all have a great time!