I'll second what Belle Ella says. With some races I'll run together start to finish and others split off based on our times and training. A lot of it depends on how different my pace/conditioning level is to the person I'm running with. If it's dramatically different, the faster one can accidentally push the slower one too far, too fast and make the end of the race hard.
Talk about it up front and have a plan so that noone feels badly at the end. I've decided that my non-Disney races are for time and my Disney races are for fun and silliness.
For my mom's first half, I paced her (at the pace she specified) for the first 6 miles, then left her so that I didn't push her beyond her limits. For my first half, a friend did the same for me and we met up after the finish.
If it's a first for both of you and you're more interested in finishing than the time, I'd say stick together, get the pictures and enjoy yourselves! I did this for the Princess Half with a good friend when we were both too hurt to actually run the full race. She was recovering from pneumonia and I had a dislocated tibia (don't recommend doing that, BTW). We stopped at most of the picture stops, walked when we felt like it, ran when we felt good and finished a full hour slower than our normal Half times, but had a blast anyway. The coolest thing is that we have those pics of us crossing the finish line together. We run the same races a lot, but it's only one of two finish line pics we have together.
Like the Snow and Merida, not really into the fairies that much either; I've worn RT's Hook shirt the past couple of years so probably stick w/ that one. 
If anyone didn't get it, I can email it to you.
