First couple about to go on a honeymoon

I have NRaas Traveler and some other mods installed, so my game might behave a bit differently around the edges, but then again, I haven't changed the defaults settings or otherwise messed with the vanilla game setup. With that caveat out of the way:

• When your sims go on vacation, the rest of the family will be unplayable and their portraits unselectable. No one ages during a vacation, either those who travel or those left at home, so when the couple returns, time in the homeworld will resume exactly at the point where the travel loading screen kicked in when your sims left. Needs get reset to whatever the game thinks is appropriate.
  
• You can only buy nectar makers and racks at the nectary in France. (Or through buydebug, if you feel like cheating.) All grape varieties are also available in France, but you need a higher visa level to buy the better ones from the special merchant. The nectary has some grapevines on the property, as well as apple and lime trees, but I think only the common grapes are planted there.
  
• You can, however, pick all types of grapes in the basement of Landgraab Chateau. I accessed it through an opportunity chain that started in China (something something go to the dragon cave), so I'm not sure if this is a feasible approach for your first trip.
  
• Again, if you feel like skipping steps, you can use buydebug to plant the rare grapes at home, or maybe at the nectary if you only want to half-cheat.
  
• In France, there's a house that's initially owned by the Pivert family (northeast of the graveyard) that has three trees—one each of plum, pomegranate, and pomelo. There's also an island where the rare grapes grow, accessible either by zeneport or through a tomb. No further spoilers, unless you want to know. I think that cherries are only buyable in China.
  
• Seeds show up in WA worlds the same way they do at home. You might get lucky and pick up some good ones.
  
• Island Paradise is a problem no matter how powerful a computer you have. It's the strain on the game engine from all the routing fails and other issues that causes the lag. ciane fixed up the world and made her work available as a downloadable save. As far as vacationing in the fixed version, it's certainly doable with mods in play, but I'm not totally clear on how to make it work. Even without mods, you could start a new game there and see much better results, or you could fix the world yourself by following ciane's instructions.
  

(ninja'd again)

Just to emphasize though, you cannot vacation your sims in Isla Paradiso unless you use mods. It is a homeworld, not a vacation world.

Also I think cherries can be found in both Egypt and China but all of the other WA harvestables (if you have infinite patience to find them all) are in France.

Excellent information @puzzlezaddict! My honeymooners did go to Egypt and are on their second day there. Thanks for the information on the winery in France. I had totally forgotten about that. I think the heir will go there with her husband (yet to be chosen).

Note that my Sim found some cherries and pomegranate on the food merchant in Egypt. And his wife found a plum tree. So the garden will be getting some new additions!

I think I will let Island Paradise sit for a long while. I was really only thinking of it as a vacation destination but it sounds like I can just enjoy China, Egypt and France just fine and dandy.