In reply to your question on "cubes". The BML feeding plan is very specific and the amount of the frozen mixture to offer is one tablespoon per glider per night. Check the rest of the instructions to be sure you have them down pat. http://www.angelfire.com/nb/sugarglider/leadbeat.html
It sounds like you have the basic set up going along just fine. Other than your wheel, fleece set, water bottle and feeding station you may want to pick up some 'glider safe' toys. This would include anything that they can't get a nail caught in (rope, certain cloth, etc.) Wood is discouraged due to urine saturation. Small toddler toys are a favorite. Little army men or barrel full of monkeys type things to hang from the bars for them to knock down. "Reset" toys like that are a favorite. They tend to find a favorite toy...a little plastic bracelet or monkey and you'll find that they've taken it into the pouch with them. You can purchase toy sets online...but many people have a lot of fun rummaging through the dollar store for items that work. Plastic vines/flowers. Plastic shot glasses for foraging. A tupperware full of pom poms and fleece scraps as a foraging box. Put "toys" up in the search bar here and see what you come up with.
Have FUN with it and they will too. It's also good to change the cage up every once in awhile...get's boring in there, you know?