I don't know about "ease preparing" a session, but I had a three year game where I used all kinds of things like this (board games, card games, dice games, games I just made up off the top of my head...). Almost every session we would have some "downtime" where we would all eat dinner in character, and we would usually have a mini-game. In my experience, it was a huge hit. The players loved the little break.
It also got them to flesh out their characters even more. When the only roleplay occurs during moments of battle, suspense, or seriousness, then a whole side of that character gets neglected.
Of course, the sessions for this game were very long (usually Friday night through Sunday morning), so we had time to do things like this. But even if you don't have a ton of time, it's not hard to throw in a quick 10 minute interlude to play slots, a quick game of blackjack, or something like that, give some in-game rewards (or penalties), and move on. For a good example of this, there are lots of James Bond-like films that have the secret agent playing a game of Poker or Blackjack while talking to another agent or other contact (posing as a card dealer, of course), winning quickly with a stroke of genious, and moving on throughout the casino to go find the nefarious mob...