I have been on two trips to Nepal with my daughter. We were a party of 2 only. The first was Annapurna classic trek in October.This was a perfect time as we had clear blue skies nearly every day. There is one high pass to go over 5400m (which can get snow any time of the year and block your way), but we travel from subtropical rain forest right through to semi desert at the back of the range, and it is different every day with amazing views of snowy peaks. Young people particularly enjoy this trip. The other trip we did was the Everest classic trek with EncountersNepal.com starting from Jiri (October - November), (not flying in, but going over 3 mountain ranges first to acclimatise). The local people live beside the track, as they do with the Annapurna circuit trip) so if you are interested in the Nepalese way of life, you see it below about 4000m. They cannot grow crops above that altitude. If you fly in you really only see the high mountains, and not many local people, apart from porters and guides. Also you are more likely to get altitude sickness. We went up 4 high valleys in the Everest area, each one rather different, and very beautiful. One was Everest base camp. Rishi (our guide) is about 26 age (roughly) and was honest, friendly, knew the tracks very well, and was good fun. We carried our own packs on the first trip, but hired Rishi's cousin as porter on the second. He with a few others have set up a company 2004 which has a web page which includes some photos encountersnepal.com If you have a guide he arranges all the accommodation - organises transport, knows the best tea houses, finds you the best rooms, organizes showers, etc., and even went ahead to get us a room when we otherwise might have missed out. If there are only a few of you, you are more likely to have a good trip less chance of having to turn back due to sickness, can go at your own speed. The trouble with walking in a group of 12 is you get very little contact with local people, so it's hard to learn about their view of the world.