Heading to Costa Rica at end of Jan with hubbie and our two year old. We'd like to be in a toddler-friendly environment near or on beach.
I will mention and recommend a few from the many that I have stayed in. The Guanacaste area of Costa Rica is very famous for its outstanding hotels. Starting with Jw Marriott Guanacaste Resort & Spa, Westin Playa Conchal, Flamingo Beach Resort & Spa, Four Seasons Resort Costa Rica At Peninsula Papagayo, among many others. If you don't want to drive many hours, you can choose the Jaco or Playa Hermosa where there are so many nice hotels as well, Marriott Los Sueños Ocean & Golf Resort, Punta Leona. All of them are toddler-friendly resorts.
Hope this helps!!
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I stay at the Riu Guanacaste All Inclusive in July for a wedding. It was a nice resort and very family friendly. I saw tons of families staying there and they had plenty of offerings for entertainment for kiddos. A beautiful beach and nice pool area.