You could stay at the Devonshire Arms - is the wedding really in Ilkley or at Bolton Abbey - which is on the Devonshire Estate. There's a fitness club across the road. Sheep all around and a lovely walk to the River Wharfe.
Craiglands is the biggest hotel in Ilkley - the internet access was a phone jack in the hall last time we went - 2005 - its a big wedding reception hotel.
I actually like the little hotel by the river - about 30 years ago it had a reputation for hooligans - but I stayed there last year and the proprietor assured me they'd all gone and we had a very quiet and pleasant stay there - its not your 5-star - but its clean and comfy with coffee in your room. There was an older clientele in the bar and all was quite civilized! Check out the Riverside Hotel. You'll meet real locals and have a Yorkshire experience there. The public swimming pool which is not that great is not too far away across the river - and you can watch the local cricket there.
You can take a walk alongside the river and see an old Pack Horse bridge - its also not far from the Parish Church and the Olicana (Roman name for Ilkley) little folk museum.
If you want something convenient to Leeds and Bradford Airport try the Chevin Lodge near Yeadon - its in the woods and the lakes were made in the war - I can't remember if bombs were tested in them - but there's a story there. It has wooden, modern huts that are quiet.
Rombalds Hotel is OK - also a Best Western now - and close to the moors - you can hike up to the White Wells for your morning fresh air or the tarn or the Cow and Calf!
I wouldn't recommend the Crescent unless you want to be on a busy corner in the middle of the town's busiest junction.
As another writer says - there are many places up the Dales - Heddon has a good pub for eating. Buck Inn in Wharfedale, etc.
Of course if you don't want a local Yorkshire feeling and want to be in a 4-5 star hotel that could be anywhere in the world then stay in the middle of Leeds and take the train to Ilkley, There's the Queens Hotel right next to the railway station - the old railway hotel. Its been renovated over the years and you can shop at Harvey Nichols in Leeds and go to the many Starbucks!
In Bramhope there's the Post House - its got a pool.
You could stay at an old Spa Hotel in Harrogate and taste the sulphur waters (behind the pump house there is a tap).