I've got some information for you.
You should not be scared about sending a seat via mail to Europe as long as it's properly packaged. I send tons of Swedish rear facing seats all over the world and so far zero damages. Some seats are tougher to package than others, like IziKid X1 which required double box and special care of foot prop, but I usually include the original plastic wrap from manufacturers and then wrap seat in three layers of bubble wrap. In some cases I also custom cut the box. A box with less empty space tends to hold up better. I then surround the box with way too much packing tape
) Some boxes get a bit beaten up but it doesn't matter since seat is still so well protected.
I guess a seat could still get damaged if hit by a truck. Seats I ship have made it to far away places such as New Zealand, Australia, US, China and of course also all over EUrope without issues.
About car seats as checked luggage. I've done lots of trips with my young kids and always brought the seats and checked them as lugggage. I use special padded car seat bags which are padded additionally with diapers and clothing. 50+ flights and so far no issues (knock on woood....)
In case you want to transport your Radian as checked luggage you could keep it in the original box and pack it as recommended above. Before you bring it to the airport, carefully check dimensions of the box so you don't get hit by some huge fee.
I really don't know which alternative is better. To me both alternatives would be fine as long as you pack the seat well. FYI, when seats are delivered to stores there is no bubble wrap or anything else included (at least here). It's just the seat in a thin cardboard box.
Nothing wrong with a Radian, it will be illegal to use one in Europe but you will honestly not get stopped by anyone.
There are plenty of other alternatives available to you. You have access to all the great rear facing high weight Swedish seats which will allow you to keep your son rear facing for a very long time. The Swedish seats allow rear facing to 55 lbs (25 kg) and are very easy to install. They are also certified for Europe, ECE R44.
Most common seats are Britax Two-Way, Britax Hi-Way, Britax Multi Tech, Maxi Cosi Mobi, Brio Zento, and IziKid. All these seats allow rf to 55 lbs except IziKid which only does 40 lbs. This seat is especially in demand in Ireland and UK.
If you don't have your own car, Britax Hi-Way or Two-Way would be a great choice.
Hi-Way: Rear facing only to 55 lbs. A light seat which takes teh least amount of room of all Swedish seat, is relatively lightweight,a nd comfortable. It's also the easiest seat to isntall. I've had ours installed in 10-15 cars, taxis, limos, vans, and freinds cars wtihout issues. Seat shell is like most other Swedish seats 57 cm (22.5 inches) which ulsually allows rear facing to about 4 years of age or a little longer. My son made it to 4 despite being tall.
Two-Way: Unique combination seat popular with foreigners, especially Americans. Allows rear facing to 55 lbs and forward facing with seat belt to 55 lbs (as a high back booster). it's also the only European seat which allows forward facing to 55 lbs with harness. Seat shell is 60 cm. (24 inches) which usually means rear facing until age 4-5. Seat does not have a foot prop and is easy to install. It fits fine ins amller cars such as Peugeot 208.
Those with larger kids usually choose Multi Tech since it has the highest seat shell at 62 cm (24.5 inches) but is expandable to 68 cm. The high seat shell means rear facing to age 5-6 if desired. This seat can also be used forward facing as a high back booster until 55 lbs or with harness to 40 lbs.
Not sure about bringing them on a plane, I would advice not doing so. Regarding safety on a plane, all data shows it's almost unheard of for a child to be injured in air by turbulence etc. You will also run into problems depending on which airline you use. In US you must use an approved FAA seat which will most likely not work with many other airlines internationally. Especially not in Europe. Sadly, the rules for parents wanting to bring seats on planes are very confusing (and unclear) and it's difficult to know what applies when flying internationally (or even domestically)
I think it's "fine" to use a sat illegally if it offers a large safety difference. But there are other (easier) choices than importing a seat from US which are equally safe.
If you need more info about the Swedish rear facing/combo seats, please ask here, send me a PM, or email me at
ad@adventuredad.com I can provide photos of kids sitting in different seats if needed.