Keto diet - carb up help

Hi, I would really like a bit of advice. I have been on a ketogenic diet for 6 months now. The reason is that I was sick of yo-yo dieting whilst wasting muscle and struggling to maintain my weight. I teach and train in karate and was not eating enough protein and had wasted quite a lot of muscle mass. Because if the dieting I had messed up my metabolism and if I ate I gained weighed. I was a slim fat person!! A nutritionist told me to try this as a way of eating and not gaining weight (I do plan on introducing carbs again slowly when I get to where I want to be). It’s really worked for me. I’ve gained 3kg of weight since starting the diet but my body fat % has gone from 34% to 21%
I tend to do targeted keto as I don’t like to be out for long and I also start craving sweets if I do a full day of carbs! I workout a lot (daily) and although I probably aren’t as good as I would be if I had carbs I don’t mind to not be able to do quite as many press ups etc. The thing is I am doing to Yorkshire 3 peaks at the end of June which is a 26 mile walk climbing 3 mountains.

I would really appreciate some advice on how much I will need to carb up for this. I don’t want my muscles to pack in halfway!! I am doing Tough Mudder in August which I plan to do a full 48 hours carb up for but I was wondering if I will need to do that for this or if I could get away with doing a bit less. Like I said I don’t like being out for too long! Any advice is much appreciated