The challenge is keeping the Solio charged so you can charge the iPad. I had a similar challenge trying to keep an iPhone 3GS charged. Eventually, a combo of a Solio (an older model) and PowerDuo battery packs worked well.
I brought the Solio charged. Then, charged with the solio. Then as PowerDuo battery. Then the Solio (when it was charged again)
Unfortunatly, the PowerDuo batteries don't work with the iPad.
I hope this help. I look forward to hearing how your Solio works for you.