You cope because you have to! You'll soon get into the swing of things. I'd thoroughly recommend a pump if you can get one, they can do much smaller doses than pens which is great for little ones, and you can do all sorts of tricks with them which you couldn’t possibly do with injections which fine tune things much more precisely and make it a lot easier to deal with things such as illness, exercise, slow digesting foods, birthday parties etc. They are not an instant fix and do need a lot of hard work, but worth it in my opinion, and your little one will soon get used to wearing it, we told our daughter it had to be her new best friend!
Regarding testing through the night, a lot of people don’t and you'll probably be told you don't need to. We were told that, and that if she does go low in the night it would wake her up. But then once when we were doing a lot of overnight basal testing, we discovered that she often dropped low at night and it didn’t wake her up, and as it didn’t happen every night it took ages to work out why it was happening and how to avoid it. Then when we got the Libre we discovered that she was sometimes low for 3 hours and still didn’t wake up! So I’ve carried on doing night testing, only once though sometime between midnight and 3 am, and if she's ok then I leave her alone. If you're testing many times through the night I would suggest that you need some help to get things more stable, but the occasional random check I can understand! If you can get a CGM which alarms when they are dropping then that should make things easier, we're hoping to get that with daughter's next pump. My daughter is 14 now, and probably won’t want me barging into her room at night much longer, and tbh is much less likely to drop at night these days so I could probably stop the night checks now, when she's an adult I will have to leave her alone! But at the moment she wants me to continue, I think it makes her feel safe.
School - find out who your son's teacher will be and arrange a meeting before school starts. Our school always has at least one inset day before the children go back so try to make use of that. Go in and explain things to the teacher and don’t move until you’re happy that they have understood at least the basics. Make a care plan - your DSN can probably help with that initially - it's basically a list of instructions for how you want everything dealt with, i.e. mealtime procedure, how to spot and deal with a hypo, what to do if they go high etc etc. Schools are very variable unfortunately, some are brilliant and listen to you and get it nailed, others less so unfortunately. The DSNs can go in and speak to people for you if you’re struggling. Fingers crossed yours is one of the good ones!
My daughter was diagnosed at the very end of year 1 and spent the last 3 days of term in hospital, we then had the 6 weeks holidays to get to grips with it and then had to send her into year 2 as a diabetic, so I know exactly how you feel! Good luck with it all 🙂