Thank you all for your recommendations! Thank you for also mentioning the RoadID, I hadn't thought of it, but I'm going to order one for both DD and DH.

VASLP - she runs with a running club (non-competitive, just for fun and fitness), but they don't do any 5Ks together. We're friends with her coach, so her coach ran the last 5K with her to give her hints (like don't try to race the crowd at the start line, how to deal with hills, etc.). She loves to run and does it every chance she can get. She plays soccer and is one of the only kids that enjoys running laps.

littlebear - My main reason for wanting to get her a pacing watch is so that she doesn't try to run too fast. She has a tendency to try to sprint when she gets excited and especially if there are other kids there. I'm hoping that it will help her learn what her "right" pace feels like.