Havent written about the M7 cycleway despite me riding it quite a bit over the years, reason being its not really much of a family bike ride. But if the young ones are getting bigger and wanting to push their distances, this is a good option.
Its 40km from end to end, Casula to Seven Hills, so a return lap will give you 80 big ones completely off road, without even a crossing to worry about.
I would hesitate to call it hilly, but it does undulate in the north and just south of the middle. Total ascent for return trip is about 700+m, which isnt too bad over 80km. This is not really hilly for fit adults, but kids would probably have a different opinion.
There isnt much shade apart from regular underpasses, so it can be quite brutal during the day, so early mornings or evenings are best. It actually has lighting all the way along, so you can ride it at night if you like without any lights. The could be useful for other riders to see you though.
Ive never seen it crowded, but there are always a few other riders plugging along to say hi too.
If you are coming from afar, there is a Bunnings near to both ends which have parked in on occasion, so you can get 40km then saussie sizzle, then return with another saussie sizzle at the other end. What more could you need?
Well some water perhaps... Of which there is some at the halfway mark just near the M4. If you head north, it can be a long return trip trip as there is nothing at the end of the cycleway itself. The bunnings and Hungry jacks are another kilometre or so over the hill. So stop, drink up and fill up. Its a good spot to chat to other cyclists.
Easy to ride with the trailer and the tandem, but travel prepared.