Sorry to hear about your son! Hopefully your son wasn't in ketoacidosis by the time he was diagnosed, and the initial days were just training and not ICU.
My own experience with using the Dexcom G4 CGM with my 1-year old son was extremely negative. First, it was terrible to insert the sensor -- it is a clunky mechanism which would sometimes fail and leave you with a worthless sensor, and at best would leave your child in screaming pain for minutes afterwards. The sensors would often fail, or start falling off long before their 7-day promised lifespan. The adhesive caused allergic reactions which left nasty red welts, and eventually you run out of fresh places to insert them.
When they were working at their best, you would have a readout which would tell you approximate glucose level, and if you are heading up or down. However, there are no error bars, and errors can be very significant. More calibration (measuring with a strip and entering the measurement into the CGM) is not always better. Sometimes we would find it was exactly correct, sometimes it would be 50 or more points off. You still always have to measure before dosing because the accuracy just isn't there.
The biggest issue we would have is, leaving the CGM under the crib so that it was in-range, and then checking it during the night, many times we would end up with the dreaded '???' in place of a blood sugar reading, and a large gap in the chart. Dexcom blamed the CGM and replaced it twice; the problem kept recurring.
Then, the times when the CGM was not losing its mind or its signal, it would frequently start false alarming -- it does not have a hysteresis algorithm to prevent the alarm from triggering over and over again if you are lingering and constantly crossing over a threshold. As anyone with a young child knows, sleep is a priceless commodity, and unnecessary alarms going off multiple times throughout the night are a total deal breaker.
For a system which was supposed to increase glucose control and peace of mind, the G4, for our 1-year old and us, did neither. Add in the extreme cost ($350/mo for sensors, assuming they all even work) the utility just wasn't there for us. Two G4 Platinums and a few sensors now sit in the back of the closet collecting dust.
We used syringes for almost a year before switching to the OmniPod pump. It is similar physically to the G4 sensor, except it auto-inserts the cannula which helps a lot, although our youngest still cries for a couple minutes after each insertion (every 3 days). A controller acts as the glucose monitor, and also lets you enter in the carbs and it calculates the appropriate bolus. It's a nice system, except the pods also fail early about 20% of the time, they can fall off and leave rashes and puncture wounds, and they waste a huge amount of insulin for children since the minimum capacity for a 3-day pod is nearly 100 units. But it's hard to beat the convenience of dosing for a meal when you're eating out and you just have to push a few buttons.