I don’t know about the practicalities, but it’s a great place to visit.
Unlike PDS they do, do it till the death though. They usually open when there’s snow on the ground and by the end of the season all bar the first lift will be closed, it’s not too much of an issue I’d say there’s more than enough to ride for a weekend.
It’ll be colder than summer and possibly wet, but I rode the bike park in the pouring rain and apart from the complete and utter lack of other riders it was pretty much the same, the flow trails are hardpack almost mirror smooth, way more so than say BPW so you rarely see any mud.
Looking at your costs and the times it’s not massively different to flying to Geneva from the UK for a weekend in Morzine, I’d have no problem doing that.
The only reason to say no would be a better alternative as above.