Excuse the intrusion by a non-ATCO but a long haul fam flight is probably only useful in terms of seeing somewhere nice for a couple of days. You'll see a bit of UK/Euro ATC (all to a high but familiar standard), maybe some transatlantic HF stuff (frankly a bit dull) and then how not to do it at a foreign port. If time is short then sitting in on a sim check with one of the participating airlines may be a beneficial thing. I have had ATCOs sitting in on my checks at BA and the experience has been mutually beneficial, particularly to me in a subsequent airborne emergency.
On the other hand if you really want to go somewhere nice then keep lobbying. You're always welcome on my flights and I'll even save you the best crew meal!
Edited to add are there any more TRUCE sessions coming up at Swanwick?