all glass sliding doors can be locked. sorry can't be more help. we just returned from our stay. we stayed in a regular beach pool villa and all doors that lead to outside - wood and glass can be locked. the glass doors if locked can only opened from the inside (there's a little flap you lift up/down to allow the door to slide). while theoretically kids could do it, i highly doubt they would be able to 1) figure it out if you don't show them and 2) have the strength to open the sliding door - it's pretty heavy.
the wood entrance door opens with a regular key.
we saw one family with smallish kids - about 5-7yo but that's its. there were two families with teenagers.
be advised there's almost nothing suitable to little kids - no kids club, no kids menu. they do maybe one or two short-ish activities per day for kids but that's it. Food - highly advise to be on all-inclusive for kids as there is not much kid-friendly food (by american standards - don't know what your kids are used to). There's always chicken, steak, fish etc for lunch and dinner but paying $50 for a dish your kids will take two bites from is ouch...there's also nothing in a way of snacks - just things you can order from room service but are like regular dishes (appertizers, mains, etc). at breakfast, there's not much you can take with you for later - an appple and an orange.
happy to answer any other questions. but i would think twice about taking small kids to this resort.