New to diabetes

I am new to the whole diabetes thing.  Our grandson was diagnosed 3 weeks ago.  He is 5 years old and has the most amazing attitude I have ever seen.  He is very open about having diabetes and very cooperative about his blood sugar testing and his frequent shots.  He is with us a great deal, so I have had to learn along with our son.  The newest info he learned at his diabetes class at the hospital is that his son doesn't have to have a certain number of carbs aat each meal, as he was required to do the first 3 weeks, but that the insulin can be adjusted according to the number of carbs.  Since I learned one way and now am relearning, can someone elplain this to me?  He gets 3 shots of humalog daily and one shot of Lantus in the evening. 

His endocrinologist will give him an insulin to carb ratio, something like 1:15. That means that for every 15 grams of carbohydrate he eats, he should take one unit of insulin. His ratio will be different, and the endo will have more info than that, but that's the basics.

That will only refer to his rapid acting, humalog. The lantus dose should stay the same every day.