Depending on the ability of the senior, you can set up the iPad with Face ID and Siri so all they would have to do is open the iPad, look at it, then say “Siri, Call Phillip (or whomever) on Skype.” You can find many more tips for folks with special needs if you go to Settings > Accessibility.
Again, depending on the senior’s mental capacity, you may want to consider Guided Access which limits the device to a single app and lets you control which features are available. This might prevent your senior from replying to spam emails and messages. And it would definitely stop an outsider from accessing other apps and possibly causing complications. On that note, I would definitely recommend NOT setting access to any financial, banking or credit cards. I believe you can set up an Apple ID without a credit card. Check here:
How to create a new Apple ID - Apple Support
But if you must enter one, maybe set up a new credit card with a VERY LOW credit limit and one that will notify you if it is used without the card present. I would not recommend using a debit card.
I’m sure others in this forum will have more good advice to add. I commend you for your efforts in doing this. It could be a welcome window to the world for your senior.