My son will be 10 tomorrow. He was diagnosed three weeks ago. It's been quite a journey for our whole family- one with ups and downs!
First, get sleep. You're unlikely to do anything wrong or get any hypos in that first week. Get rest, take stock and get into the habits of the new routines. There's a lot to organise and learn - from how to get extra supplies for school to how to count carbs. Don't rush, write lists and tick off a few each day. I took quite a lot of time off work (which is now catching up on me with that stress...)
Your son needs it not all to be about diabetes, but if you're like me, your head is spinning with all you're learning about diabetes! This is not easy. I tried to find ways to have normality as often as possible- we went for a walk, we went to the cinema (finding a 15g carb bag of posh popcorn).
I also got him back to school on a Friday afternoon- a short couple of hours that let him be reassured his friends still wanted to play with him without the pressure on us or the school of a whole day or week.
Our school has 4 children with diabetes, but it still wasn't easy as he was doing things differently from the others (who are all on pumps, while he's injecting). The afterschool club got really nervous. In both cases it helped for the hospital nurse to come into school and afterschool club to teach and train them. It seemed to me that there was always one more barrier to prevent the afterschool club taking him and I was exhausted about trying to get all that in place (just as I was trying also to return to work and catch up with having got so behind when I was fully off work)
At your stage I was scared about hypos, so let me say that after three hypos (in his second week) he was already sufficiently aware to tell me when we was having one.
Be gentle with yourself-you're doing better than you think. Sleep, rest and take your time.
Warning also that my son has had several major emotional upsets last week (our third week). It's now fully hit him that this is for life. He was so sensible and matter of fact about it in the beginning... the outbursts have been frightening for me (lots of "my life isn't worth living" and even "if it's autoimmune then it's my own body's fault and I'm punishing myself".). I held him, agreed it was really tough, told him I loved him as he is and I'm with him through this. I didn't try to pretend those emotions were wrong. (After all I've cried too and that's with an adult brain not a little boy's brain - because however mature he can be, underneath he's still a little boy). Those outbursts have been contained and he has got back to getting on with it. But afterwards I'm drained. (I had to cancel a 9:30am meeting after one awful before-school outburst, there was no way I was ready to work ...)
Use the hospital team - the nurse will help you work out doses, the dietician will help with carb counting and I've also had an appointment with the family therapist who is helping me deal with both my son's emotions and some of those underneath family frustrations that have been there for years...
Good luck.