Nice start, if you keep the wiggly-worm track plan, stick to the hook and loop couplers.I would actually suggest keeping it so the kids have a specific place to run "their" trains, while your running "your" trains on the mainline. I would also recommend cement morter the tunnel together nice and firm, lest one of the kids accidently sends the blocks tumbling onto the tracks (and trains)! Kids tend to use similar such items as diving boards, intentionall or unintentionally, when kids are playing they tend to forget the things they are bouncing off of can be damaged.