Travel
Option 1 from Paris
Flight
Avianca
Avianca links Paris to La Paz through Bogota. This is probably the best option given you stop at 2600m high - it's not a bad idea (although not strictly necessary) to allow for a 24h/48h stay over in Bogota to allow a gradual acclimatization.
Flight
Boliviana de Aviacion
BoA is the Bolivian airlines. It connects Madrid to Bolivia through Santa Cruz. This is probably the best option for our Spanish travellers. From Santa Cruz, you will need to take a short 1 hour flight to climb the mountain up to LaPaz.
Hotel
Casa Grande Hotel
Hotel
Atix Hotel
For all the days along the way