I'll gladly think of a few options. :)
For example option 1:
DAY 1:
- Euskotren to Hendaye
- Intercités Hendaye - Toulouse-Matabiau 10:20 - 14:26 1.60€ optional reservation
- TGV Toulouse-Matabiau - Lyon Part-Dieu 15:38 - 19:50 20€
DAY 2:
- TGV Lyon Part-Dieu - Lille-Europe 11:00 - 14:24 20€
- IC Lille-Flandres - Kortrijk - Antwerpen-Centraal 15:09 - 17:38
- hourly IC Direct into the Netherlands
Let's try to avoid Paris during the Olympics. You could also do:
DAY 1:
- Euskotren
- TER Hendaye - Bordeaux St-Jean 10:09 - 12:42
- TGV Bordeaux St-Jean - Lille-Europe 12:58 - 17:58 20€ (book soon)
- sleep in Lille
DAY 2:
- relax via Kortrijk and Antwerp (or Brussels)
Feel free to ask anything! :)