Yes, Pedialyte would avoid an electrolyte deficiency on a long fast but if you do, this will lead to other deficiencies.
To explain: if you take any external nutrition such as this on a fast, the body will believe it is in "eating mode" as opposed to "fasting mode" and will make little if any effort in conserving its other stores of nutrients; this in turn will lead to deficiencies of one kind or another whether that be of Essential fatty acids and vitamins and so on.
Glad to hear that your diet has been of a good quality, but the amount of fat reserves one has is not always a reliable indicator of how long anyone can safely fast. Dr J Fuhrman MD abandoned his fast on day 46 because of an electrolyte deficiency (he had the benefit of Lab' results and testing) despite ample fat reserves still available to him.
The other problem with possible electrolyte deficiency symptoms is that they can closely resemble the symptoms of detox, and therefore difficult to distinguish between the two.
My advice would be to take the fast one day at a time rather than have a set number of days and where hopefully you have a BP/pulse monitor to hand every morning on arising for accurate readings.
An annual fast of 15 days or so is and was quite the norm among Natural Hygienists as a cleansing measure, so good idea. Healing is better served with a body that is free from toxemia. My own first fast of 25 days was entirely detoxification and not pleasant, but my second of 30 days was plain sailing and hugely enjoyable.
Fat burning or ketosis occurs in the body when glucose/glycogen stores have been mostly depleted; this occurs within the first 2 to 3 days, so it just isn't correct that eating a fatty meal just prior to your fast will bring on fat-burning more quickly, unfortunately for those who wish to lose weight in the shortest time.
I wish you every success with your goals and keep us informed/updated as to your progress. Please report on any unusual symptoms if they occur.