There isn’t that much intricacy connecting expansion zones to previous content. The mission board in the city should suggest to you some options relevant to your level, and when you pass 60 and 80 you’ll get a quest delivered via drone (apparently) which asks you to choose Outland or Northrend, and then Cataclysm or Pandaria.
There are however portals to these places in your capital. At least, there definitely is for Pandaria, and I assume there is for other expansion starter zones. For Outland, just head for the dark portal and find the questgiver outside it. Northrend can be reached by boat from the Stormwind docks.
The raids… the raids will be a problem. Basically nobody does them. You can quite easily go back on a level 120 and solo them, but freezing a character and doing a raid for the right level? Very few do that.
That said…
We are considering a bunch of alts, frozen at 80, going for an achievement in an Ulduar raid. If that’s a thing you’re interested in, join us, say hello 