I must be missing something here... the key words are "five year old"
Just my opinion, but if I were setting something like this up for a 5 year old (been there, done that), I would design it in two phases. Sketch out and design the complete setup in all fastrack then:
Build phase 1: inside loop, outside loop located in the same position they would be in if the switches were there. No switches. At 5, kids want to see trains go around the track, not switching, yards, etc. Add buildings scenery etc, keeping in mind that phase 2 may follow!
If you use Fastrack, when the child gets older...
Add phase 2: the switches can be swapped in. Remove a 10" section and put the switch(es) in. no other changes needed.
As I said, it's just MHO but I really think the interest level is way different at age 5 than at 8 or 9. Feel free to ignore my thoughts, just offering an option based on seeing 5 year olds and trains! Moving trains, sound, smoke... that's what they seem to respond to.
