In reply to BattyMilk:
What Cal.Mac said - especially about load limits. You can use wider bars (and bang your head on them!), the limit is as follows (having googled it before on this forum):
"The projection of a load on a trailer or roof-rack may be up to 305mm on either side of the vehicle or trailer, provided that the overall width of the vehicle or trailer (including projections) does not exceed 2.9m."
Above that, you're an abnormal load and you'll need to involve the police. Best not to go wider than the wing mirrors, really.
Pretty sure you could do it, but you might have to take the pedal off the kayak side. I would personally work on 2 boats + 1 bike on the roof and the other bike in the car, if that's possible.
I recommend WhispBar racks - similar initial outlay to Thule, but MUCH cheaper to change foot pack when you change car. Have a bit of adjustment if you want to go a bit wider than standard. You'll need T-track fittings for the bike racks/uprights.
https://www.roofbox.co.uk/