That budget gives you a decent amount of choices.

Xtabi is laid back...no worries...also try The Oasis, I have heard good things...Seastar staff send people there when they are full...'nuff said in my book...Sunset on the Beach...Coral Seas Garden...

White Sands is a great value on the 7 mile...I am sure you'll get more/better advice from more-experienced boardies...but keep in mind the Spring Break college crowd will be on the beach section during that time...may not be so ""laid back" in terms of later at nite etc...

Have a great trip!