Day trip to Isle of Wight to use gold card...

My gold card expires end of July and I must have been one of the last lucky few to get the 6 free tickets.
I intend to use one to travel from Motspur Park to IOW, but assume I need to book ferry or hovercraft separately? Ideally want to combine with trip on Steam railway too. What is the cheapest crossing? Apart from swimming! Season is Ryde St. Johns road to Ryde Esplanade.

You should be able to book through tickets to any IoW station via either Wightlink (catamaran) or Hovertravel. However some posters on here have reported problems booking through tickets recently. See the "Chippenham to Lake" thread on this forum for more details.
There's little difference in price or overall time between the two crossing routes.
Journey planners will only show stops at Smallbrook Junction when the steam line is running.

I don't think the SWTrains free ticket is valid on either the hovercraft or catamaran.
The hovercraft does sell inclusive packages with IOW attractions. Have a look at hovertravel.co.uk and then look for the combination tickets to the steam railway.