If this is all about the kids, it’s tough to say. Do they get frustrated easily? Are they athletic? Some kids have a natural ability to pick up snowboarding fairly easy. Also, if you’re only going to attempt snow boarding once, I would say don’t bother. Stick to snow tubing/sledding. It’s much easier to have fun and the chances of getting hurt are minimal.
I’ve rented equipment locally and at the slopes. Local rentals are a bit cheaper. But, it is more of a hassle. Another huge downside of renting locally: You are stuck with whatever size boots you rented. If your kids have never been skiing/snowboarding, it’s tough to get the right size boots. It depends on how thick your socks are, if you tuck pant legs into the boots, etc. They may feel fine when you try them on at the rental place, but after one trip down the hill you realize they are killing your feet/ankles and are the wrong size. If you rent at the resort, you can just swap them out – no extra charge.
Layer the clothing and use some kind of “shell” that will keep them dry.
For a day of skiing, bring your own food. It will be cheaper and better than what you get while up there.