In 2026 we are planning to book La Belle Vie (Rhone) and Blue Danube river cruise itineraries. Our available time windows are April and October. Which is the best season to do each of them? We are thinking the Rhone would be warmer in the Spring and water levels might be better in the Danube in October...so La Belle Vie in April and Blue Danube in October is the way we are leaning. Would appreciate any advice regarding which cruise to do when. Thanks!