Club La Costa

We're thinking of joining at Platinum level, costing around US$50,000 - any advice?

Sounds pretty good, just joined myself, quality is second to none. However push for as much as you can get, I got the 1st year's maintenance free, 8 months reduced payments on the loan plus a bonus week to get me started. If you have any doubts ask about the destinations club (3 year trial) they will back this back off you and even throw some additional money your way.