Hey there,
Keep in mind total free hours you have on heroku with the free plan. Even if you keep your app alive, you'll spend all hours within the month. At least that was some time ago, not sure how it is now.
you need like 24x30 =720 hours to be all active all month and you have, what, 600 hours free. If you add a credit card details (no charge), it will add 400 hours and you'll have total 1000h/mo.
Also, take into the consideration if you spin 2x dynos on single account, it can lead to charging you, because you'll be over those 1000 free hours (2x720). This is some experience from the past, don't know how it is now.
And I would recommend heroku, too.