For me, they were really worth doing! Our kids were 7 and 3 this year and, like you, we had never gone into the evening shows before (other than in the skyline pavilion). I had never felt that the 1-hour+ queue to get decent seats was worth it for children who would probably be over tired and wanting to go to bed!
Like you, I need decent seats. I'm partially sighted and don't see well at all in low light. I don't have a hope of seeing my kids in a 'nightclub' style environment, and need them to be able to see well from where I am sitting. Also, I couldn't cope with having to find a seat in the midst of an enormous crowd of people that had gone in before me. I would have been eligible for disabled early entry anyway (as is anyone with a disability). However, my eyesight is generally ok for navigating in decent light, so I felt that buying the passes was far less hassle.
Reds is slightly smaller and more 'nightclub' like than Centre Stage which is more like a theatre (or bingo hall). Both have sticky carpets, and dance floors that you wouldn't want to let your children sit on to watch a show and a vague odour of stale beer and vomit.
The doors open 45 minutes before the show starts (60 minutes for B-line pass holders). We were worried about the kids coping with a 1 hour wait for the shows - particularly the magic show which didn't start until 8pm (30 mins past normal bedtime). However, the red coats put on a great kids disco while we were waiting.
Which site are you going to?