I do a LOT of tech work for older people and I have learned a few things over the last few years of tablets taking off.
1. It doesn't matter what OS they start on, it will become the one they understand if they haven't used one before. I've had several customers that started with apple products that cant figure out android and just as many the other way around. Even if you weren't forced into it with the price point I would go android for savings now AND later.
2. Screen size matters, with most older folks the bigger the better. I get two complaints about 7" tablets #1 "I can't see the little stuff on the screen"
3. and #2 is users of many of the "cheap" 7" tablets have performance complaints when browsing their favorite websites.
That Nextbook 8" honestly looks like a very good choice for the money or as mentioned above the Kindle Fire HD is a good device to consider and it has a more basic UI out of the box that may be a pro or a con.
i7-4930K/GA-X79-UP4/32GB G.Skill & Team Vulcan Mixed/512GB Crucial M550 SSD/240GB Seagate 600 SSD/3TB/R9 290X/GTX 750Ti/Rosewill Capstone 750 (main rig)
i7-4770K/GA-Z87X-UD5H/16GB ADATA/240GB Seagate 600 SSD/3TB/2 x 1TB RAID 1/1.5TB/HD 7850 2GB/Rosewill Capstone 750-M (secondary rig)
i7-4810MQ/Sager N8258-S/16GB/2 x 480GB Crucial M500 mSATA/2 x 1TB/GTX 880M/180W AC Adapter w/8 cell battery (gaming laptop)
i5-4300Y/Dell Venue 11 Pro/8GB/256GB Sandisk M.2 SSD/Intel HD 4200 (GT2)/25W Ac Adapter w/removable 2 cell battery (Win 8 Pro Tablet)
i5-3570K/GA-Z77X-UD5H/16GB Kingston HyperX/500GB/3 x 2TB/2 x 1TB RAID 1/Antec BP550 (server)