Hmm, I think the Arenal Volcano area probably might not have that many "great hotels" nearby. Along the Western coast of Costa Rica there are a good number of really excellent resorts and hotels worth going to.

There's the Four Seasons, which is really in a class by itself. And two others that stand out in my mind and have gotten good press are Paradisus Playa Conchal, which is almost as pricey as the Four Seasons, and Hotel Punta Islita.

Panama's hotels are still up and coming. The best bet I think you'd find there is The Bristol, which actually used to be part of Starwood's Luxury Collection and is still, I think, a Leading Hotel of the World. The Bristol is in Panama City and would be a good home base. Unfortunately, I've no recommendations for the day trip in the canal or other sights off the top of my head, but if I remember any I'll post again. I second bailey's hotel recommendations for Costa Rica too.

Costa Rica has a lot to offer. Stay in a Jungle Lodge in Tortuguero National Park in this lush rainforest setting and experience the sights and sounds of the birds and monkeys. To add to your adventure, take the canal nature tour. You can go to Arenal Volcano region for hiking and horseback riding. Enjoy one the beautiful Guanacaste beaches in the Pacific Coast. Tamarindo Beach is known for the thousands of sea turtles that come seasonally to lay their eggs. As for the hotels, Tabacon Resort in Arenal and Fonda Vela in Monteverde although are not considered luxury, they offer maximum comfort and rest. In Panama Ciy the Bristol hotel definitely is one of the best, so the Intercontinental Miramar Panama. I am not sure about the boat ride. You can book it with the tour operator though. I can recommend you Latour company that I’ve been using. They can take care of your hotels as well. Thing to see in Panama: the cruise to Gatun Lake, the native authentic Indian villages and the rain forest along the canal.