Well...you have some significant hurdles there! All the more amazing to see where God takes you!
We started in a similar rectangular carpeted room. The following purchases made the environment soooo much better... We created a "stage" with a brightly colored rug & put a portable screen behind it. I ran all the media through my laptop with a portable projector & small speakers. Using portable rolling walls, we create 5 small "pods" around the perimeter of the room for small group space. Using each corner of the room, as well as the back wall, these small circular spaces felt like little small group "forts"! Each space had a small rug as a focal point to lay out materials and gather around (sitting on the floor). We also put a funky Ikea lamp in each one so we could lower the lights during small group times. The kids love the "club house" feel & the lowered lights & group separation helped our small group leaders keep focus & create some group dynamics. We used the center of the rooms for any larger games.
As far as services for adults go...when we cannot find a regular small group leader,our strategy is to pair leaders and had them trade one month on - one month off. Leadership stays consistent through each vitue, and over time many of those paired sg leaders build "team teaching" relationships and communicated regularly with each other regarding thier small group. On the month they serve,our media team makes a DVD of the adult service available to them. DVD's were ready to go home with them by the time pack everything up. Not everyone takes advantage of the DVD's, but for those who are truly hung up about missing service, it is appreciated.