I'm a former Flight Attendant and I fly transatlantics a lot with my three children. Just some points;
1. Good risk-assessment on the lap held infant issue. No, they are not protected if anything goes wrong BUT there is very little chance of that. Some parents are comfortable with that idea. Others are not. There are children who would have survived if they had been in a car seat but the numbers are very low and some are disputed...
I've seen some really uncomfortable flights with large toddlers but there is only one of her and two of you. This is a much better situation than if you were alone and/or were flying with more children.
Just to clarify, she is NOT turning 2 during your trip. The FAA is strict about the child having not had his or her 2nd birthday before flying. I had an incident once with a toddler who had his birthday while in the U.S.
2. Not only is it NOT true that "we'd all die anyway", most people
survive crashes these days. Just having that attitude could increase your chances of
not being one of them. Little things, like knowing which exit to head to can save your life. Links? No. These details are not shared with the public. We learned of person X who panicked and did Y in recurrent emergency training, but those stories were not released to the press for obvious reasons.
3. Flying a foreign company does not increase your chances of an open seat. In fact, if they don't let you use your car seat, than it's not a good idea. I always try to book U.S. companies because we fly with a car seat and I don't want it taken away or be forced to check it. Very aggravating! Parents on foreign companies don't have the same rights as they do when flying a FAA carrier. For your information, Lufthansa is among the better ones, if you can't book a U.S. company.
Code shares are just for marketing and doesn't change the laws of the country whose company you're flying. Check for a small mention of "operated by..." or look up the flight number on the airlines' own site.
4. Not sure if baggage is an issue but if you purchase an extra seat, she'll have the full baggage allowance. If your husband is bringing a lot of goodies back to his family, you might want to look into it. I'll also assume you need your car seat with you when you arrive in CR. Having it on board means it wont get lost or broken en route.
5. Looking at flights that are leaving now, high season, to predict how full they'll be next October isn't really relevant. October is usually a pretty quiet month for transatlantic flights. There is a school vacation around Nov. 1st in much of Europe (especially in Catholic countries) and there can be some big conferences that month but both are easy to avoid. Weather is unlikely to cause problems then too. I think you'd have a fighting chance of a free seat then, says someone who worked these flights for over 10 years.
This is just a recommendation but it's much easier to connect in Europe, especially with children. Try to get something non-stop to Europe and connect there. You usually arrive in the morning, meaning that you have all day to get to Prague if your transatlantic is late. Coming back, that means getting through Customs and Immigration without the stress of still catching a domestic flight (think delays again). Do NOT take this advice if it really cranks up the price of the ticket or causes other inconveniences. If all else is equal...
There are often children's discounts on transatlantics so shop around. I usually do better with an agent but just go all routes; agent and on the net, look on both the consolidation sites as well as the airlines' own sites.
Here are my non-commercial flying tips. This is a 10 year old article I wrote for an expat newsletter way back when and many parents have contributed (including some here);
http://flyingwithchildren1.blogspot.com
October is a good time to come over here. Prague is beautiful and take advantage of the fact she's not yet in school!
P.S. That article needs updating. The FAA now allows seats to be used at any age, as long as it's per the manufacturers' instructions. Not relevant to this discussion but wanted to mention it.