P&O have a 12 day cruise to Canaries to/from Southampton leaving 2 Nov. Alternatively,if you want somewhere warmer, you could sail out to the Carribean via Canaries on either 24 or 31 Oct and fly back, 15 or 16 days. Have a look on www.pocruises.com, but book through a travel agent/cruise club for cheaper prices.
I would have no hesitation, even if you only have a week, and choose the Caribbean. Pick a good cruise line, four or five stars, and if you can afford it get a cabin with a balcony and immerse yourself in the warm, happy, luscious atmosphere of the Caribbean....Id.
A 50th deserves a bit of luxury - have a look at Celebrity, Azamara or Seabourn.