When you say 'young' daughters, how young are we talking? If they are old enough to provide their own thoughts I'd ask them what they want to see in the layout and make sure you include that. One thing is for certain is that I strongly recommend all operating accessories be within their reach to make sure the play value is optimized. I would also recommend changing your design to better incorporate the accessories more along the lines of what you would see in the real world. Additionally, I would think long and hard about using your current design as those crossovers just get in the way. Remove them and you could create a layout when you can run trains on independent areas of track - you could have 1 mainline loop and a separate switching line to work all the accessories. Heck, you could probably sneak in a double mainline. Now if your thing is to just watch trains run all over the layout then by all means go with what you have. There's more than one way to enjoy the hobby.
-Greg
