I'm afraid Drakes Drum's advice is absolutely correct.
My extra advice would be:
Leave the soccer boots behind - I assume they are the heaviest items. Many kids here play in bare feet anyway! (Bring some money to buy second hand boots if they are needed.)
Wear as much as you can of your own clothes (DD has very good advice on this too!!!). Keep the weight of your own things as low as you can. Eg - no need to carry soap etc.
Go to the Airport overweight. Talk nicely to the check in person and say why you are taking all that stuff (if asked). You never know - the next person in line may be under weight. The chances of your getting through with all you have is very high. (I've only once had problems and that was in Switzerland!!) Whoever takes you to the Airport should carry a bag to take items home. If they see you are serious you may well be let through!
And of course you can pay for XS baggage!
Please don't post anything. I've even lost books in the mail.
The recipients have to pay a charge for presentation to Customs, then tax and VAT.... The total can be more than the value of the things - if they arrive at all.
Second hand clothes are very easy to buy here and cheap.
It is heart-breaking when folks want to bring things to give away.
You could also try appealing to the top Management of the Airline and you can point out that Kenya Airways gives two bags of 23kg each from UK.