Tinysalmon I took DD to my native Stockholm when she was just two months, for Christmas. No problem at all. Did lots of travelling in DD's first year when I was off on maternity leave. In fact, the smaller they are, the easier it is to travel! especially if you breastfeed. No need to bring loads of gear, just their sleeping bag, clothes and your boob, they're not even really into toys when they're that small. The only thing I'd avoid is somewhere with loads of worrying tropical diseases, such as malaria prone places etc. Not even heat is a problem, just make sure they're hydrated and in the shade mainly, took DD to Georgia (the country) in the summertime when she was 9 months and she loved it, just slept a bit more due to heat, but that gave me time to chill out.
Travel all you can while they're under 2 and they go for free on planes (well, there's a small fee, but not like buying a full price seat), I'd say! Now when DD is coming up to two years, it's so tiring to travel with her, she hates sitting still on the plane and makes a huge fuss and wants to run up and down the aisle. I have to ply her with iPad and sweets, something I normally try to avoid, but on the plane it's full on Peppa Pig and limitless supplies of raisins!