I do a combo of those things. For existing clientelle I raise my fees by $1 per day, every single year. And, for anyone coming into the daycare as a newbie I start them off at my next anticipated fee increase rate.
So, for example, I am now at $42 a day. Anyone new coming is right now will pay that fee as well. But anyone I take, this year, after, say, about June, will be paying the January 2015 rate of $43 a day. And, in January, all my existing clients will be bumped up to $43.
This has always worked for me. And we SHOULD be giving ourselves a raise either by increasing fees for existing clients or charging more to new clients EVERY year because inflation increases every year. And that means you are actually making LESS money every year that you DON'T raise your rates. That loaf of bread you feed the dckids goes up so you should recoup that cost by passing it on to the parents because it's THEIR kid. You can not work year after year and take home LESS money. That would be the dumbest, and worst business plan ever.