Good grief! I wash my two every week!! Definitely don't waste money on dry cleaning!
Do the buttons up, check there is nothing festering in the pockets and then I put it in, right side out, on a 30 degree wash for about 40 minutes, just with detergent (no softener or Vanish type stuff).
I wash the tie as well (even though it says dry clean only - no problem). As soon as it is done, get it out of washing machine and hang it on a proper suit jacket hanger - on a day like today I would put it outside to air dry a bit - normal week it hangs up vaguely near a radiator - they dry very quickly - I have been known to chuck it in and hang it out ready for the next day...
Your son is likely to grow out of it before it wears out!!
....and Yamin....they go back on Tuesday....
I wouldn't dry clean jacket either. Tie always gets slung in with the rest, no problem, and yes, I know they go back on Tuesday, but our washing takes all day to dry in this weather and need time to curse and try and make it look like a vaguely normal blazer again!!!!