Various places. Mine are now 5 and 6 years, been travelling with them since newborn. We have done backpacking in Vietnam, city European breaks, visit to Japan, weekends in newyork.
All between 3-4 days and 2-3 months long trips.
This summer I did a short 2 week road trip with them. France, Italy, Croatia. Flew down, hired car in France, dropped car in Dubrovnik at the end and flew back from there. Just went on small hikes, to the beach, took some boat trips, sightsee a bit, ate out. They made some friends along route.
Depends what you both want to do really. If your travelling alone I wouldn't recommend going somewhere where women's rights are rubbish as you won't have the freedom to book anywhere or drive etc.
Europe is probably the best starting point if you want to travel alone for a longer time. You can get a car, drive between various locations staying as long or short as you like. And can always fly from locations to further locations temporarily using mainland Europe as a base. Can get some great skiing there done with him if you are in the mountains Jan-April