Here are some other suggestions. Check out this post I made in another thread
http://www.costaricaticas.com/phpBB2/viewtopic.php?p=72445&highlight=wing#72445. It was in reference to a newbie question about splitting rooms at the SL. I really don't know if any of the lower priced rooms have more than one bed. I know the penthouse has 3, but that wouldn't be any real cost saving. What I suggested was that they take the basic rooms there which are all in one wing and just share bathrooms.
Of course, that thread did not raise the possibility of the Amistad as an alternative. The 3 rooms in the Clubhouse wing would run you about $150/nt + tax vs. the $90-110/nt + tax for 2 rooms at the Amistad (depending on whether you go for std or dlx). Is that worth the extra money for everyone to have their own rooms in a decidedly chica friendly hotel? My guess would be yes, but I don't know your friends. How high on their priority list is mongering versus more traditional tourism. If they're new to scene or only borderline committed to mongering, they may prefer a more mainstream environment of the Amistad to the hardcore monger atmosphere at the SL. Yet another possible solution would be to let them split a room at the Amistad, while you get your own room at the SL. The cost is a factor to them not you and the 2 hotels are only 100m apart.
If you really want everyone to stay at the SL and your friends still balk because of price, why not make a friendly bet with them that, after seeing the chicas that hang out at the SL, if they're not glad you chose that hotel for them, you will split the difference in hotel costs. That might be a bit of a gamble depending on how honest your friends are.