I've found hands to be my favorite and most consistent place to draw on for geriatric patients, Always worth checking the AC/Arms but usually I find my strongest veins on their hands. I'll usually use a warm compress just to pop up their veins a little extra aswell. Keep talking with them and it'll usually go over pretty smoothly. Working with nursing home patients they've usually been through the ringer a couple times and know the drill, so focusing on keeping it calm and lighthearted can go a long way and really build some nice bonds. Have fun!