As mentioned, Volcano National Park lava activity is a hit or miss/luck of the draw contingency. Our past four visits to the area have been disappointments; on one ocassion, missing spectacular action by less than two weeks...but, in years (many) gone-by, we've had experiences bordering on overwhelming.
As a first steo in your decision making process, here are reliable sources of information:
Periodic updates by the USGS - hvo.wr.usgs.gov/activity/kilaueastatus.php
and a number of webcams -
An excellent, though sporadic, blog; Hawaiian Lava Daily -
Also, an ongoing thread here on Trip Advisor -
To get to Volcano National Park, you'll need to fly from Kahului to Hilo on the Big Island. Clouds permitting, the flight is among the most scenic in all of Hawaii; passing along southeastern Maui, including Hana, and the north east coast of the Big Island. Hawaiian Airlines offers reserved seating; if at all possible, you might want to consider reserving "E seats" on rows between 4 & 10. This will afford each of you a window seat, in front of the right wing. On the way back to Maui, try for seats A. In consideration of your daughter's special needs, I'd recommend a helicopter tour...if you think all involved would be at ease with such a flight. We took our autistic son on four flights and I truly believe he was never more focused and in touch with his surroundings; I only wish we had the opportunity to take him just one more time...
Anyway, the helicopters fill-up quickly when the lava flows are active. Once/if you decide to take a tour, reserve immediately; several companies (but not all) allow full refund cancellations. Blue Hawaiian flys the most comfortable of the tour helicopters, the Eco-Star and 100% refunds upon notice more than 24 hours in advance. Their website includes this policy and video clips ( bluehawaiian.com/bigisland/… ). Also, Blue has excellent video capability of your actual flight; numerous exterior cams + one in the passenger compartment.
At the other end of the helicopter excitement spectrum are "doors-off" Magnum P I type helicopters. If of potential interest, I'll be happy to discuss the companies with which we have flown.
If time/budget permit, an overnight stay would allow the opportunity to explore the park and, Madam Pele permitting, offer the chance to see night-time lava flows from a distance; all-in-all a truly memorable experience.
Sure hope everythinbg falls into place for both of you and Vicky.
P.S. PBS produced a wonderful video that you might enjoy (be patient; there is a preliminary 30 second commercial), but afterwards, it's 50+ very entertaining minutes (be sure and enlarge via the button at the lower right of the screen):