I think to encourage some extra involvement, we could do something similar to the "52 weeks of cooking." Where every week (or we could even do month) there is a tying theme. Some examples could be "foot binding", "soaring", "business casual" etc.
That (good) sex does not start in the bedroom! Foreplay begins waaay earlier with flirting, reducing stress and chores, compliments, caring acts etc. The bedroom is just the ending for a lot of long term couples.
The other thing is that sex will change significantly throughout your relationship.