You don't want games that require an internet connection to be active while you play. So, for instance, "Words with Friends" wouldn't work for this purpose. You need things that work offline.
Most solitaire games for phones/tablets have several variants in one app; so if you get bored with one option you can move to another. Do try to play a bit ahead of time; some "offline" games give you easy levels that will keep you busy for 20 minutes or so, then make it literally impossible to win any further levels without spending extra money to buy special tools or point bundles to get past the next level. That would frustrate the heck out of you if you purposely bought the game to stay entertained for several hours.
I find that games I pay a bit for upfront (usually less than $3) are much more satisfying in general than the so-called "free" versions are in the long run, because they don't bother you so much with ads and in-app purchases. I would advise buying either an iTunes or Google Play gift card to upload to buy if you want, so that your real credit card is not linked to the app store, since you're not likely to go out there often enough to monitor it well and make sure no one has hacked your account. I have an Android, and I bought a $20 Google Play gift card for this purpose 4 years ago; it still has $2 left on it. I have 3 phone games I tend to play whilst traveling, and one of them is solitaire; I don't have much interest in gaming beyond these few "kill a few minutes" types of games, and I won't buy "extra" value features in-app, either; if the basic version of the game doesn't keep my interest, I delete it.
Also, btw, if your public library offers Overdrive &/or HooplaDigital, you can download ebooks, audiobooks, and some movies & TV shows free of charge. Be sure to take along a comfortable set of headphones that work with your phone, and if necessary, a power bank to renew your charge.