Welcome to the forum!
First off, in case you haven't seen it, this book is free to download & has a ton of up-to-date info, I'd definitely recommend checking it out - http://www.westcoasthedgehogs.com/fi.../download.html
Your cage size sounds good, & liners are great!
I wouldn't recommend using sand at all, personally. There's a couple of people who have tried using it on the forum, but if you have fine sand, it could easily irritate the eyes and nose, and any sand would be a risk for getting caught in privates, especially for males. If you're looking for something for a dig box, many people use fleece strips or a small container with small aquarium stones.
For transportation, you need a hard-sided cat or dog carrier. It's the best way to transport hedgies safely & make sure they're protected in case of a car accident. If you're unable to respond, the emergency responders are trained to look for animal carriers after the people are taken care of. You can put a fleece blanket or two in the carrier for hedgie to snuggle up in during the ride, they will probably sleep the whole time, unless they get car sick.