Whilst the crowne plaza isn't the one bang opposite the station, it is pretty central - about 5 mins from the station.
Will echo Trinity for brilliant clothes shopping and family friendly eating. The lovely mexican place is cielo blanco, plus there is a carluccios, giraffe, wagammas etc. Can also suggest some independents if that is up your street?
I would definitely make the most of the connectivity from Leeds station. Perhaps investigate getting a weekly pass for zones 1-4 which will cover a lot of the suggestions previously posted - www.wymetro.com.
One of my favourite places is Bolton abbey. Beautiful walks, lovely old ruined abbey, nice tea room, small pebble beach for a paddle - and can get the bus: www.dalesbus.org/cravenlink/
There is a new art space, the tetley, that has done children's craft activities in the past - it's near Leeds Dock, home of the aforementioned mumtaz.
You can walk along the canal to kirkstall abbey - or get the train out to bingley, see the five rise locks and walk along to saltaire (again to echo well worth a visit) before getting train back to Leeds. Actually, you may be able to hire bikes from Leeds station cycle hub and the can is great for cycling along.
There is a sculpture museum next to the gallery and the ysp will be well worth the trip.
Everyman cinema is pricey but a lovely treat, or the vue in the light.
Lotherton hall for bird gardens, thwaites water mill I've heard good things about, Roundhay park always a winner...
Enjoy our great city!