There are two "accessible" playgrounds in the Harrisburg area. The older of the two is Possibility Place, located off the Paxtonia exit of I-81 in Harrisburg. The newer playground is Adventure Zone Park, located at Capital Area Christian Church on Lambs Gap Road in Mechanicsburg.
Both playgrounds are built on a rubberized surface and include ramps to get to all sections of the play structure. Having visited Adventure Zone (AZ) fairly regularly, I am more familiar with its in and outs, and overall have enjoyed it more. AZ has a separate "tot" section, supposedly designed for children 2-5. My 2-year-olds, however, being the adventurous sort, outgrew that side almost as quickly as they could walk. I now spend my time at the park supervising their clamoring up the cargo net and ladders on the "big kids" side. There is a sand box on the tot side, which usually contains quite a few kids.
Possibility Place (PP) was built first, and was either not built as well, or is showing its age early. There are places where the rubberized flooring is buckling already. Also, when we were there, the park was VERY crowded, and I heard from a lady at AZ that there are day cares that use PP on a regular basis, keeping it crowded. The one plus to PP is that there are shaded benches for the parents within the playground. There is no shade at all at AZ, except for within the picnic pavilion.
As with other parks, AZ starts to get crowded around 10 a.m., so if you have early risers and kids who've given up their morning nap, it's a great place to be early in the morning. Also - it's cooler!
There are great picnic pavilions at both parks, with full bathroom facilities. (I think, I haven't actually used them, but they look nice from the outside!) The picnic pavilion at AZ is also available to rent; there are fliers at the park with information, or I'm sure you could look on the website or call the church.