A:Since it's your first time, I'd suggest the London Eye for sure. The panoramic views are fabulous and both of you would enjoy it. The tricky part is doing it on a day and time when you've got good sunshine and the lines aren't too long.
We also found Hampton Court to be a nice place to visit on a sunny day with all of the gardens and flowers in full bloom. It's only a 25 minute train ride from Waterloo station.