dont forget you may need a carnet for each of the bikes. I understand the rules around taking your bikes on a trailer into the EU are not well defined and subject to local interpretation at the minute. You may need a carnet because you "could" be exporting the bikes if on a trailer. It would be ok if you were actually riding them.
A belligerent customs officer could turn you back or charge you to take the bikes into the EU.
I have read that it shouldnt apply to a road registered bike but may do to a race bike???? which isnt road registered. However there appears to be some confusion at the borders and it can be a bit of a lottery. There was an article in adventure bike rider saying as much. might be a challenge to argue with a mis informed customs guard.
We are taking road bikes so we should be OK on the carnet front but I guess if the worst happened we could take them off the trailer and ride them through customs
I have been advised that the white reflectors should be fitted to the front of the mudguards.
Another thing I have learnt that is new for me anyways is that we need CE approved gloves - all to do with knuckle protection apparently.
Plus of course, reflective strips around our helmets, reflective vests reachable without dismounting, etc etc