We would advise you to:
Take with you possible gifts for schools ( e.g. pencils, exercise books, picture books ) - better than money
Take with you any spare walking gear you could leave with your guide / porter
Ensure you have adequate protection for your eyes and skin ( particularly if trekking high )
Use a wide-necked water container rather than a camelbak
Take a ' buff ' with you and / or a scarf
Take ear plugs for the barking dogs at night!

We would advise you not to:
Give to beggars - sadly, it encourages a dependency culture ... but it's hard to do
Buy plastic bottles of water
Use post boxes ... the safe place to post letters / cards in Kathmandu is Pilgrim's Bookshop in Thamel!