Help me GM with mixed player styles

Hi folks! I'll get straight to the point.

One of my players has a boyfriend who's played for a long time, so she has a lot of resources to draw on when creating her characters in terms of optimization. My other players are newbies who don't know the ropes well enough to even contemplate optimization. I'm looking for advice on how to design encounters that will be challenging and interesting for the whole party. How do I keep one character with an optimal build from outshining her companions, yet still let that player feel rewarded for her extra effort?

Extra info: I'm a relatively inexperienced GM. To be honest, I'm a relatively inexperienced player too, with only fifteen sessions or so under my belt (including 4E and 3.5E but mostly PFRPG). So don't be afraid to break it down for me :)

Extra extra info: The party makeup is as follows - Ranger 5 (archer with owl companion), Wizard 5 (evocation school), Monk 5 (utterly new player), and Magus 5 (the optimizer). I realize there is no healer, but that was their choice and I'm making custom dungeons so I should be able to work with it.

I've been that player (the most experienced) in my group, and my partner is brand new to the game.

Step 1: Ask the optimizer not to overly optimize. This is the most important. Ask her to try and keep her power level even around the other PCs.

Step 2: Design encounters for the average-powered group members. If the Magus outshines (it's very likely she will, if she tries to go shocking grasp route), go back to step 1. Or, power up the other PCs if step 1 is not working.

Step 3: Include "new rules" into some of your encounters. Make the encounters a fun way to learn some rules. Make monsters that rely heavily on trip, and have the PCs learn CMB/CMD. Or an encounter where they can bull-rush people off a cliff, etc. Find fun ways to introduce new rules whenever you can.

Step 4: Include battles that will reward good tactics. Hint to your PCs to use terrain to their advantage. Have them find a camp as they crest a hill; being above your opponent gives you +1. Teach them how to use a bottleneck against large numbers of creatures.

Step 5: Allow your lesser experienced players to "trade out" old feats or character choices as they progress in power, and maybe realize some of the cool things they could do.

Step 6: Profit.

Optional: Step 7: Set up a "battle arena" on an off night where they can bring legal characters of whatever level (ex: level 5) to duke it out. This will encourage lots of new things, as well as get them to read up on new classes, feats, etc.

If the newer players are looking at the optimised characters efficiency and effectiveness with envy (which is healthy) have a session where the girl's boyfriend comes along and everyone spends some time optimising each other characters (helping to make their characters more effective not different characters).

If the newer players are thinking the optimised character is against the spirit of the game try and make them see that it takes all types. Sometimes you just have a group that doesn't want to play the same game.

Have they already created characters?

I would have part of the first session be creating characters if they have not already created the characters. Perhaps the optimizer can assist the newer players and all work together to see how they might fit together.

They already have established characters (except the monk, but I did help him make his already). We completed part 1 of the Kingmaker AP, and I'm moving us away from that because there are too many extra rules to learn.