I agree with Kettering Northants QC that 7 nights is a very long time to spend in KL. You'd be better off going somewhere else for a few days. As for KL, the RC has been my favorite hotel there for a while now. I didn't like the Westin mostly due to the weird "casual" look they're going for; it just doesn't work. If you do go to the Westin, get one of the bigger rooms as the basic rooms feel cramped. My second choice in KL would be the MO.

As for the Cameron Highlands, be aware that it's a bit of a drive going up on serpentine roads. I enjoyed driving there but a lot of people don't. If you go there, the Cameron Highlands Resort is your only choice (it has a very good spa I am told). Service is great, but its location on the main road makes it pretty noisy. If you live in a temperate/cold climate there's really not much point going to the Cameron Highlands, as its main attraction is the cool temperatures. It makes for a decent respite if you live in the tropics though, or if you like tea, strawberries and mock Tudor scenery. I enjoyed it but it may not be optimal for your annual vacation. If you do go for RC in KL and CHR in the highlands, sign up for YTL Platinum Plus at 50 MYR for additional benefits.

Other options for a few nights: try a resort at Penang (e.g. Shangri-La), spend a few days in Singapore or even Phuket.