I am currently running a druid tank, warrior dps, warlock, mage and a paladin healer and I can tell you a boomkin is dead weight. They don't have the mana to keep up fights and will run out mid fight and not having a wand leaves them useless.

In your case I would prob go druid tank, paladin healer, spriest, mage, lock. Or go 1 melee, 1 tank, healer, 2 ranged but you said you did not want to go that route. Healing on druid is mostly just spamming full heals as the hots are quite expensive for the little healing they do. Paladin healing is quite easy as they have very few skills to be decent healers.

On the druid tank I can tell you it is viable, even though most people won't believe you but druids are the best tank in MC in pre-raid gear and do fine in dungeons. Paladins on the other hand are a little tricky since they don't have a taunt, meaning if you ever lose threat to your clothies, you better have bubble on speed-dial or they will die pretty fast.

I would also advice against a mixed comp if you never done so, especially in classic as it is a lot harder then it is on retail to manage different classes in my opinion. It would be a lot easier to get a known working comp like tank/healer 3x mages to get to know how to handle 5 toons, work out your setup and optimize it and then try a mixed comp later on.

On the end-game part. I picked a mixed group because I could not decide what I wanted to main, and warrior, druid and warlock are on the list. Mage is there for food and portals and paladin as healer since he is most mana-efficient of all the healers. And they bring blessings (5 min sucks but they do keep mana rolling). It is a lot harder, but it gives you more options later down the line but you do have to get there before burning out.

Also, if you only have an hour an day, I would again advice you to pick a zerg group otherwise you won't be able to finish most dungeons.