On our first visit to the Big Island, we plan to stay 3-4 nights in the Volcano area, and then drive to the Kohala Coast to snorkel and relax another few days.... Mauna Lani was recommended, but unfortunately it is closed; any other suggestions for hotels, condos, etc. near snorkeling areas, or within a short drive? Thank you!

We've rented a condo in the Waikoloa Beach area a couple of times. I found the location convenient for both driving to Hapuna and Mauna Kea beaches, but also going further south for snorkeling at Two Step. We ended up driving every day, anyway, and this was a good spot for us.

The Fairmont Orchid might be the same price range as Mauna Lani:

https://www.fairmont.com/orchid-hawaii/media/photos/

Yes, the Fairmont looks good... and now trip is back on as I just moved it up a bit and the prices have dropped substantially!!

Any recommendations for where to stay in the Volcano area??

IMO, you have too many nights in Volcano (there are many lodging options there, but most are b&b or vrbo type). There's now only one stop to look over into the caldera (at Steam Vents; an hour at most), and Chain of Craters could be explored in the same day. Hilo would be a better option for that part of the island (25 minute drive up to the park).
I agree that Waikoloa resort is an excellent choice for condos ranging from approx. $120 to luxury, plus the Marriott and Hilton, with nearby amenities such as shopping, restaurants, food court, and A-bay, and easy access to the Kohala coast (north and south) with its archaeological sites, beaches, and scenery.

Thanks for all the tips; My trip is in early Sept. 8 days, and has changed a bit in the itinerary....

Now
1 night Hilo (arrive 8 p.m.)
or 2 nights Volcano House or Kilauea Lodge
Drive to Kohala Coast
then either Westin Orchid, or Mauna Lani Point condos... they're the same price though food will be higher at the Orchid for sure... though will have a frighted at least.
the Waikoloa was priced much more...
Then either commute 1 1/2 hours one way to Capt. Cooke area to snorkel at Kealakekua Bay or stay 2 nights at nearby Sheraton, not an inspiring hotel, I know.
airport and home. Any thoughts?? Thanks again

Lost a long reply, so I'll make it brief this time.
Better, IMO to stay in Hilo on arrival, don't go up to VNP in the dark. Early start, easy drive to the park. Later, explore Hilo and surrounds (waterfalls, gardens, drive along the ocean, Banyon Drive, zoo, etc.) The Hilo Bay Cafe is a nice place for lunch, with lovely views, or the open air Pineapples in town is tasty and fun.
We love the drive (scenic and easy) to/from Kohala coast via Saddle Road (with a stop at Kaumana Cave State Park), but the Hamakua coast drive (Belt Highway) is beautiful, and has many places to stop (Onomea Bay scenic bypass, Akaka Falls, Lapahoehoe park, all stunning).
Also IMO, the Capt Cook snorkeling tours (several combine stops at Kealakekua and Two-Step, or Honaunau) are an excellent way to avoid the drive and problematic parking and access to Kealakekua. Lots of good options leaving from the Kona area harbors (lots of coupons), just a much easier way to do Capt Cook. If you decide to visit Place of Refuge (Honaunau, Two Step) on your own (as we did after going by boat), get an early start to avoid rush hour traffic (it can be bad), because parking can be difficult. (You can park in the Place of Refuge National Monument lot if you are visiting the site, which is well worth a trip in its own right.)
Surprised you found Mauna Lani lodging at a better rate(!) than one of the many Waikoloa Resort area options, but it's a quick drive for a beach day at A-Bay and/or fast food (or a DQ Blizzard fix).