Keep the trampoline until the kids (or you) no longer use it! Oddly enough I kind of like the bed of Pine needles because it almost looks like mulch, and its free! I agree that you will have to fight to keep your lawn alive unless you're out there everyday raking out all the needles.

If you want a hard surface, I would stay away from stone mulches like riverstone, clear gravel, or decorative gravel. The needles will fall on this and get inside the stone mulch and rot, create weeds, and is even harder to keep clean. I would consider extending your patio instead and having a solid surface, whether you use concrete, pavingstone, or flagstone.

If you want to include some planting, look into plants that enjoy acidic soil like: Rhododendron, Holly, Hydrangea (not sure of your plant hardiness zone).

If you create plant beds, I would keep the pine mulch as your groundcover.

Best of luck!