It’s possible to fly into Chetumal Mexico as well but it’s a bit more expensive. The easiest and cheapest way to get down to Chetumal and Calderitas from Cancun is by autobus. There are a few autobus stations in Cancun (all of which have free WiFi) and they are quite easy to find by taxi. While in Cancun make sure you ask taxi prices up front before you get in to avoid scams or other problems.
Even if you don’t know much Spanish it’s quite easy to navigate the autobus stations and generally the people are very welcoming and helpful. Don’t be scared to try out your Spanish and ask for help! The trip by autobus is about 6 hours depending on traffic with a few stops along the way where you can get some food and snacks. It’s also possible to rent a car in Cancun but personally I prefer the autobus as you don’t have to worry about licenses, paperwork, or any government check points. (Not that it’s a problem in general but I prefer to not have to worry about it.) The further you are from Cancun the cheaper it becomes and the atmosphere is much more chill in general.
Renting a car is also quite cheap here if you decide to do that however I would highly recommend some sort of travel insurance, even just medical. You never know when an accident can happen and it’d be pretty rough spending a vacation in the hospital worrying about the bills. Considering Mexico is much cheaper when it comes to hospitals and insurance even a cheap package would go along way to protect yourself and your family. For solo / cheap traveling I recommend the autobus but if you’re coming in a group renting a car might work out better. Either way I’ve tried to find the best offers and deals to make your trip as smooth as possible and if you ever have any problems traveling this area my number is always open.
There are some fun things to do in Cancun however and if you are there for a few days I recommend checking out GoCity Cancun. They’ve got some really cool opportunities and make it really easy to get tickets to any kind of fun / entertainment you might want to enjoy. They offer a sort of pass type card so you can enjoy all kinds of adventures at a lower price without having to worry about admission and schedules. Local tours are another way to enjoy the area if you’re feeling adventurous and they can be found from Cancun to Chetumal. Tons of unique opportunities you’ll only find in Mexico!