The upcoming Mario Tennis Open was discussed in today's European Nintendo Direct, with some specifics announced on multiplayer and Mii customisation. The most significant detail for tennis players hoping to take on friends and family was the confirmed inclusion of Download Play for local multiplayer, allowing up to four players to enjoy a match from one copy of the game: no details were given on the options available in this mode, though they're sure to be more limited than full multiplayer.
The Mii customisation was fleshed out, with confirmation that there will be over 200 items to collect and apply to your character, affecting power, spin and movement. The trailer also showed a brief glimpse of tilt controls being used alongside the touchscreen, no doubt to make the game accessible to more players.
So, if you want to play friends you won't all need a copy of the game to do so. The lack of an RPG mode is apparently due to the inclusion of Mii customisation, meanwhile, so does 200 unlockable items compensate for that?