Hi, I have not been at Dzongu. However, being myself in Gurdongmar, I am suggesting you to keep Gurdongmar plan intact and then visit Maenam instead of Dzongu in following- Given you reach Ravangla from Lachen on day 3, you will have a very little to make arrangements for Maenam trek. So you can contact Diken Rai @ 7584813732 beforehand. He can make arrangements of sleeping bag, tent, foods for the whole trek only if you are planning to spend overnight at hill top. Also he himself can be the guide. You can either start for Maenam top on 19th, night stay there and return to Ravangla on 20th, or you can start very early in the morning and come back from hill top on same day. Snowfall is all luck but December will be freezing, at least expected to be. So if you are planning, to stay at hill top overnight, you must arrange tents and should not rely on the only half broken watchtower there.

I have replied your other question. Please check :)

Depends on his/her age, severity of asthma. The total distance is 12km which is continuous uphill, so you can easily understand. The only thing I can assure, it will be more than tough to do whole trek in one day though. Spending overnight at hill top will be helpful. I, personally, encourage you to go. If you don't feel okay at any point, you can stop there and return. Keep it simple. :)

My wife and I on the cusp of 70 and all our party were 65+yrs - so your folk should be OK - what about you? are you fit? Just take it slow and easy and enjoy

maenam hill is a wildlife sanctuary managed by forest department of sikkim. so, yiu have to pay a minimum entry fee n camping cost at the entry point. it is good high altitude trek n if clear u could see beautiful sunrise, rich oak forest n rhododendron forest.