Training schedule

I have officially signed up for the Oklahoma City Memorial half marathon on April 28th. I have a deadline to meet and a long distance to go. I've done 5ks and 10ks before and this will be my first half marathon. 

Oklahoma City, downtown with the Devon tower

I've baked up my own training schedule and I'd appreciate any feedback from my friends who have already done a half. I am doing one long walk a week and I've been adding half a mile each week until I reach my training goal of 16 miles. I know the half is 13.1 and my training distance will eventually be longer than that in hopes that the actual race will "feel" easier. I picked 16 because I felt is was a nice round number and just 10.2 miles short of a marathon. If all goes well, I expect to train for a marathon next. During my long walks, I am keeping my speed to a 15 minute mile. I know this is a pace I can keep for a long time. I hope to work on speed later (after 16 miles have been reached) but for now I am focusing on distance. Saturday, I went 10.21 miles and next Sunday, I'll walk 10.5 at least.

Will I be successful? Is this a decent training schedule? I'd love to hear your opinions, especially if you've done a half marathon already. Tomorrow, I'll have another tip for weight loss.