Looking for ideas on a multi tiered layout

"I have kids that will be running trains occasionally, so just being slow and careful won't cut it."   I have used a variable AC transformer for my "visitors".  It simply reduces the incoming voltage to the conventional transformer.  I just dial down the incoming voltage to the ZW transformer and let them go full throttle as much as they want.   I can adjust the variable transformer up or down depending on the load of the train or for faster engines. 

I did a "very quick rendering of 3 tiers on top of each other to show you how much you'll be covering with each level and how large the top level would need to be using 18" HO curves. As you can see, about 1/3 of your O gauge and 1/3 of the S gauge will be covered.

I then added a couple of optional views. The 2nd is a traditional "wedding cake" format. While it doesn't solve the access problem, and is more for open tables, it does provide more visibility of more track and provides greater access for your "grabber". The 3rd simply moves the middle and top levels against the end wall with the idea that you would cut an access hatch inside the left side of the ovals that you could then access from the bottom and more easily deal with problems. Even though it's not shown, an access hatch would be added to option 2.

The other thing that comes to mind is that in this limited space, I think the idea to locate the smaller gauges in the corner to "fool" the eye might not work as well as you envision. I think the 3rd option would give you a similar effect and let you do more things in the area of landscaping, removable tunnels, etc.

aussteve: I like the idea of being able to limit the throttle to visitors and kids. I have a DC locomotive that without any cars behind it will zoom around the track at incredible, unrealistic speeds. I will have to look into this.

doubledaz: I hadn't thought about your second or third option. It looks as if I widened the s gauge track by either a half or a full piece of track, then I could build the entire layout with no tunnels. Being this is my first layout and I'm on a budget, simplicity is a good thing. I also hadn't thought about an access hole under the table. (this would be a great job for the kids to climb in there and fix wrecks ) By the way, thank you for taking the time to render these for me. I've been toying with scarm for a while, but have yet to master all the features.

Just an FYI, I did those in RR-Track, not SCARM.

Don't forget that the 2nd level is not S-gauge in the examples I posted, so I don't know exactly how it will line up with level 3. But since S-gauge has 20" curves, you should be able to cut the corners off the upper tables and get 3 levels inside each other. FWIW, that is known as a "wedding cake" design. The only hidden track would be those you cover with removable tunnels/panels. Also, bear in mind that 3 simple ovals can get fairly boring pretty quickly, so you need to consider long-term interest, even more so with kids. Usually that means tunnels and switches to give them something to do besides watch trains go in circles.

No matter what you do though, remember to account for the access hatch. If you design each level to fit inside the level below it, then you won't need as much height and you'll probably be able to reach things through a hatch that goes straight up through all 3 levels. However, that depends on how high your 1st level is and how much separation you want between levels. You also need to consider how hard it will be to duck under the layout to access the hatch if the layout is too low. It's not so much to lift derailed equipment as it is to repair things that are causing problems.

FWIW, I designed something similar for myself at one point and you can find it here if you want to take a look.