I'd look at intermediate destinations and try to convert a lot of that travel to land. If they can get to India or china, train travel to get a lot closer to home becomes viable.
In the past I'd have suggested California, then cross-country to New York and the QM2 to the UK, but I would avoid the US for now for reasons.
Honestly, it sounds like their best bet is don't miss the March cruise. Best of luck.