Paddington Station

Since you are coming into the Paddington TRAIN station versus the TUBE station, there will be a Lift near Platform 1 (Unless theyve moved it!!)...Kings Cross has a lift as well.

When you are in Paddington station, you should take the little one to see the bronze Paddington Bear statue in the main concourse!!

I don't know about a lift. But in Kings Cross Station you must visit the "Platform 9 3/4" created by station employees several years ago for the benefit of the thousands of Harry Potter fans who asked directions to its location.

According to the London Transport website, there are no lifts at the Paddington Tube Station: http://tinyurl.com/dxze27

Have you considered taking the Piccadilly Line from Heathrow direct to King Cross?

I take the Piccadilli line Tube from Heathrow to the Kings Cross station. It's cheaper and easier, probably just as fast as the train/tube combo. From Heathrow to KingsX the Tube takes about an hour.

Thats correct Michael, no lifts at Paddington TUBE station, but there is one at the TRAIN station, where she will be arriving via Heathrow Express....
When one has a baby with them, every minute you spend can seem much much longer, hence, why I understand why she wants to take the Express! But the transfer to Kings Cross may be just as hectic..

It might be easier to take the little one on the bus, though it depends how much luggage you have. The 205 goes from right outside Paddington to Kings Cross every few minutes. It is operated by modern double-deckers which "kneel" at the kerb, so that you can easily get on with a pushchair. It shouldn't be too busy during the day, but at peak-time, it might not be pleasant.

Another possibility is a taxi, which will probably cost around £12, which might be good value and a lot simpler. They are easily hailed from outside of the station and will take you directly to Kings Cross in 15 minutes or so.

Mark