I am against splitting the party. Simple, more there is person between me and the enemy, more I feel good. So, I need people to buffer
For Holy smite, I won't generally be in the area of effect. But it is a good spell to throw at your paladin who is in melee. On spell that risk to affect me, it is circle of protection against evil... and it coming in a few level only.
For taking figther level, here what I advice: if you go for teh stats, wait. Get those level 3 spells (both divine and arcane spelllist are pretty cool at level 3). For a cleric, it isn't that much a necessity. There is a lot of spell that come handy for a cleric that make him as good as a figther on the short run, and with time, you'll see that you pass much time casting, so the boost in combat you took is not that great. I think the best option for a cleric who goes in the combat style is taking the war domain, but that's can be done at creation.
Now, if you go for the background. Go on! I took my sorcerer level with Sielwoodan as soon as second level, and look how often I cast spell... stats wise, it was a bad move, but I wanted Sielwoodan have his power as soon as possible, and I choose Sorcerer because he wouldn't have to carry a book with him, and he would have never spent time studying spell. Honestly, I favor style over stats, even if I am sometimes attract by stats...