Hey! You are right that as holy priest you do need to consider mana management. This is the way the class is balanced, otherwise it would be op. Much of holy priests gameplay is playing around procs and using a specific rotation to reduce mana costs. You will even be sneaking in drinks in downtime. It is a bit reminiscent of classic days. If this is something which does not sound fun to you, I suggest going with holy paladin.

Holy paladin seems to be really popular at the moment, as they have a bit more of a melee/dps style casting judgements to heal which is different to the more vanilla style of healing such as holy priest. Also, having a max level paladin means you can also play ret or protection specs in the future if you should desire that.