Some advice please

J&M

Hi ya all

Need some advice. From Jaipur we are heading over to Darjeeling area - had planned via Calcutta. Want to do the Toy Train from NJP to Darljeeling and also want to see Sikkim and Kathmandu.

But now not sure whether to stay with Darjeeling first then Sikkim and then Kathmandu and fly out from there (heading South)

or

Start in Kathmandu and go through Sikkim then Darljeeling (but want to take in the toy train heading up)

Or even better - does anyone have a completely different idea of routes?

The more I read the more confused I get so others first hand experiences/suggestions would be useful.

Time frame being a couple of weeks.

Thanks all.