First time to Panama

We are an early 60's couple planning a vacation in Panama for early April. Looking to settle in to a Panama City hotel as a base of operations - then doing some excursions such as the Canal and Gatun Lake, rainforest, Pearl Islands (thinking of an overnight or 2 there, at the end of our vacation). We like a relaxing pace with some activity - kayaking, snorkeling, moderate hiking. We like 4-star or better in terms of hotels. Length of stay would be 7 to 10 days. Would really appreciate any suggestions.