I, personally, do not care for Debbie D's practices. I think her suggested foods are often high fat/high protein. I believe she recommends something called a molasses mix? Which I really don't understand the purpose of other than lots of sugar, fat, and protein. After consulting with various rat people, they don't get all of the supplementing she suggests, either. You can give good treats that are nice and lean and that are just as good as some of the things she suggests. Also, you're feeding a decent block, which provides all of the needed vitamins and minerals that your rats need. There's really no need to supplement them for that purpose. Mostly what we do is offer variety. That's just my two cents, though.
For my girls, I get frozen veggie mixes that offer the variety without my having to go through a dozen bags of individual stuff to make it unique every night. Things like Chinese Stir fry, Japanese Stir fry, California Mix, etc.. The classic peas/carrot/corn mix isn't fantastically great, but it'll do in a pinch and the rats adore it. Depending on what I ate that night, they may get a bit of that, too. Sometimes I go a little bonkers and buy out the fresh organic produce and spend a day freezing up batches for them, but most times that just gets tossed in with the bagged mixes when I feed them. Anything from zucchini, squash, cauliflower, broccoli, brussel sprouts, sweet potatoes [always cooked!], kale, spinach.. Just about anything in the produce section is a Go. Take a peek at the
Forbidden Foods List to get an idea of what *not* to give.
As for amount, that's up to your kiddos. You want enough that it takes them a little while to finish, but not so much that there's always a bunch left over. A single green bean or so is fine, but if they're leaving the majority of their food for you to find in the morning, it's too much. If they're scarfing it down before you've even left the room, then it may be too little. I give my girls maybe 3 tablespoons total of veggies, and if I'm putting it on a salad for them it's probably less than that. Salad is approximately 1/2C of spring mix.That's enough to feed 3 females at 8mo, 1yr, and 2yrs old. This is roughly the same diet I've used for all of their lives, though. I give them maybe 1/8C of a multigrain cereal as a treat sometimes.
I personally have no issue with free feeding blocks. Rats generally don't overeat like dogs or cats will unless there are other issues. With normal, active, healthy rats they'll eat the suggested amounts of 2-3 blocks a day. I toss a handful into their bowl during cage cleaning and refill when it's empty. During the week I do daily stash checks and put everything back into their food bowl so I know they're eating as they should. It's really a personal option, though, so you do what you feel is best. So long as they're getting the required nutrition, they'll be fine.
As for the kids giving treats.. If they desperately have to give one, try to get them to offer fruits and veggies instead of real "treat" like treats. A single rice crispy or cheerio isn't going to make or break their waistline, but it can add up if all 3 are doing the same routine.