yes, don't worry about inviting adults that don't have little ones , let alone those teenagers... << they will especially become bored..
keep it small at the clubhouse, do what your budget can allow for..
even if it means ONE party and just for kids.. believe me... people will understand... before I had my son who is now nine, I NEVER wanted to attend a child's bday.. (unless I was super close to the kid) and this wasn't because I don't like kids (I adore them) it was simply because I didn't want to hang out at a kiddy function.. i took no offense to not being invited to parties of friend's who had little ones... even now, I don't take offense if I am not invited.. I understand, people have to tighten their finances and that often means, less parties and less invites..
don't sweat it..