Thanks everyone for all your wonderful advice. I see, though, I may have to expand on this itinerary a bit.

I am in southwest Florida, so it is actually easier to fly up to Atlanta than drive a couple hours over to Miami to catch an international flight - which is more logical since my daughter is in Atlanta and will be going as well. This will be a fairly short trip - one week only - with the wedding mid-week in Cardiff. Both my daughter and I will need a London "fix" of two to three days, but I haven't decided yet if that will be on the front end or the back end. Decisions, decisions LOL!

We can either land in London, get a bus or train to Cardiff, and spend a few days sightseeing around Wales and meeting the bride's family and doing London afterwards, or we get our London fix first then go up to Cardiff on Wednesday, attend the wedding and do the sightseeing after that, then return to London and fly home.

Both my daughter and I are somewhat familiar with London (hence the need for a London "fix,") but are totally clueless about Wales. I don't expect anyone to come and fetch us in London, so we'll be pretty much on our own getting to and from Cardiff.

In any event, does everyone agree that Heathrow tops Gatwick, followed by the train from Paddington? Seems simple enough, right?