Manila is not such a great place for tourists to spend 3 nights - yes there are definitely some things to do, but other cities such as Hong Kong, Bangkok and KL are definitely more tourist friendly. It probably suits the more adventurous tourist. The Peninsula is great, or if your budget permits, there is the Shangri-la also (although I consider it to be over-priced).

Maybe consider Cebu or even flying to one of the other islands (Boracay) if relaxing is something that you want to do.

What are you primary considerations for your side trip?
What other cities are on your list?