Hi Augustiner ! I spent a few months right "next door" in Nepal, and lived with a nepalese family in a village, taught in a public school. I have good ideas for gifts.
-Toys, just about any kind, most households don't have any toy what so ever. But I'd say that balls or cricket equipment would be ex-tre-me-ly appreciated by boys. Ok, it's not exactly luggage friendly, but if your mother can leave her things in a hotel where she'd be based, before heading to the remote area, and bring only the minimum there, she'd have room for sport gear. Paper and colour pencils will also make a lot of happy children.
- Jewelry, from the US or India, but she should find out before what is acceptable. I remember that in Nepal, only married women (hindu) could wear a long necklace. But Sikkim's religion is Budhism, so, I don't know.
- Warm clothes.
-If it's like in Nepal, "modern music" even from India, is almost considered as "dirty" by parents, and if fact, listening to music is like a waste of time in their mind. So no CD or cassette of any sort, I'd say.
- Skin cream ! They work long hours under the sun, and their skin becomes so dry that sometimes their hands and feet get opened wounds. Gentle soap also.
-Fabrics they can make clothes with (if she visits hindu villages, red is especially appreciated, for married women only, because it is the sacred colour). Often they have only one dress/sari, that is pretty worn out.
-For girls, also jewels, fabrics and cream.
-For guys, watches.
-For both, to the very few curious minds, they will love to receive novels in english, world atlas, etc.
Frankly, apart from warm clothing, I have no clue.
Leisure isn't part of the culture, except for children (but to some extend). I guess watches would please them.
If she wants to help out a whole community, she could contact any NGO in that area and ask what they need (notebooks and pencils, rulers, up-to-date grammar or math books, uniforms, medicine, etc.).
Hope this help !