In reply to Chewie65:
I did the Langtang + Gosaikunda Trek, EBC +3 passes (Island+Luboche Peak) and also Manaslu trek +Tsum Valley in March-May 2018.
Everest can be a bit of a faff and there are better treks to do in Nepal if you just going to EBC and back without the extras, your pals also been before so you might as well head elsewhere!
Langtang was fantastic, a real adventure (but tolerable) bus journey, a really nice intro to Himalayan trekking, easy acclimatisation, some wonderful peaks to walk up once you've got to the end of the valley, and nice options to extend the trek via Gosaikunda or take slightly alternative routes back down the valley. A real winner if you can't commit too much time to Nepal, or if you have loads of time and want to squeeze an extra adventure in!
Manaslu was very special and felt much for cultural than the other treks, it takes you through a wonderful journey of agricultural farm land, Tibetan communities (if you add Tsum Valley, which would be a must) and the views are as spectacular as the other treks. A walk to Pung Gyen Gompa swallows you with 6-7000m+ mountains, very special. You tick off a nice high pass and the diversity of terrain and geography you pass through is mind blowing and much more than any other treks imho.
I can't speak for Annapurna (so why even reply ey? ) but some friends prefered it to others and vice vera .
It really depends on what you want to get out of the trek and Nepal, where ever you go you will have a life changing experience and not regret a single decision you've made! If your pal is keen to do Annapurna and has already done Everest then go for it, you will have the time of your life! Go in the fringe seasons too...
Feel free to ping me any questions,
Dan