Since we got our son we have experienced the joys of traveling with kids. It certainly is different than traveling without but has many rewards. Our main advice is - Don't underestimate your kids! The kids do not need constant entertainment provided by hotel staff at resorts and they do actually enjoy to experience other things than the beach. Take them around to great sights, go on shorter treks, but of course take some days off for them to just play or stay at a beach also. Mix it up!
Traveling with a kid means a lot more luggage, the need for more time and costs more. On the other hand you get in touch with people so much easier with a kid, hotel staff become so much more helpful and you see a lot more smiles around you. For your own sake, it is naturally also great to have your most precious being with you sharing the experiences. Here are some practical tips and things to consider.
Packing: for shorter trips bring diapers - you will find them most places you go but we have experienced that they are not always as good quality (breathe less which easily give rashes). Wet napkins are essential but can be resupplied wherever you go. Dry napkins also. Pack only a minimum of toys - we bring his favourite teddy (actually a leopard), paper and crayons, a picture book, and small items like a spade for digging in the sand. Buying a few toys locally makes for something new and keeps their interest longer. We also bring a half litre water boiler. This is practical to sterilize teets and bottles for the very young and to cook water for making milk from powder if safe fresh milk is hard to get.
An "umbrella stroller" is a fabulous thing for smaller kids - they are easy to pack away and to drag along, and give the kids necessary rest and even sleep during excursions.
On the road: When traveling one needs to monitor the kid to adjust the pace. Where we used to take long stretches to get from A to B we now try to split this with stops and longer breaks so our son will not get too bored and tired. Big cities are normally not the best place to travel with kids. We prefer to find a smaller town with less traffic, less people and less stress as our base for exploring an area. If you're in one place for a longer time, it is better to rent an aprtment or a house than staying in a hotel. The kids enjoy this more and it is not always fun for a kid to go to restaurants three times a day, every day, and then to a pub or cafe so mom and dad can enjoy a beer in the evening. It also gives you as parents a better chance to enjoy the evenings after your kids have gone to sleep, compared to staying in a hotel room.
Many towns and cities have parks and public playgrounds that are good for kids. Here they meet other kids and get to try both familiar and sometimes new exciting activities.
Sometimes it is also worth considering hiring a taxi in stead of taking several fully crammed buses to get around to the attractions. Naturally this costs more and taking local bus can be a fun experience, so this has to be weighed against the added freedom and reduced stress of a taxi.
You can travel pretty much everywhere with a kid, but naturally you should be careful about traveling with small kids in very hot weather conditions. Most countries have great medical doctors if you should need one, but in some places the nearest one could be quite a distance away. That has to be taken into consideration when going into more remote areas - maybe you want to come back when the kid is older and stronger...
Food: it is not always easy to find agreeable and safe food for kids so you should always shop fruits and bread (and naturally bottled water). Bananas, papaya, oranges and mango are all great for kids. And always clean their hands with a wet napkin before they eat!