Only one airline flies between the two, but there is only one stop, so it’s very doable. Taca Air can get you between the two in under four hours. They go every day, and have 2 schedules a week:
Sun, Tue, Wed, Friday
Leave San Jose, Costa Rica (SJO) at 6:15 am, arrive Belize (BZE) 9:37 am
Leave BZE 12:30 pm, arrive SJO 4:05 pm
Mon, Thur, Saturday
Leave SJO 12:20 pm, arrive BZE 3:42 pm
Leave BZE 5:20 pm, arrive SJO 9:05 pm
The cost between the two is $413 round trip. It is almost the same to fly to either, so there is no advantage I can find to flying in or out of one or the other (Houston to BZE is currently $710 RT on Taca, Houston to SJO is currently $690 RT).
There is a great travel company in Costa Rica similar to us: Serendipity Adventures. They come highly recommended, and are the only other company I have found offering as many sports as we do. Why not spend a week in Belize on our island, then fly to Costa Rica and do one of their week-long trips? For example, their 7-day Costa Rica Intrepid Adventure Tour which is 7 days of horseback riding, hiking and climbing trees, rafting, rain forest, cloud forest, hiking a volcano, soaking in hot springs, and a zipline canopy tour.
Wouldn’t this be a great honeymoon? Or why not a second honeymoon if you already took one?