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Yo Souper,

My five year old brother made this deck on his own and tried it out on the GB version of Pokemon TCG. It did pretty well against grass but that's all he tried it against. It still needs quite a lot of tuning up. 
Flame of War

Energy

19 x Fire energy

Basics

1 x Charmander
1 x Vulpix
1 x Growlithe
2 x Ponyta
2 x Magmar (Base set)
1 x Magmar (Fossil)
2 x Moltres
1 x Doduo
1 x Kangaskhan
2 x Tauros
3 x Eevee
2 x Dratini

Evolutions

1 x Charmeleon
1 x Ninetails
1 x Arcanine
2 x Rapidash
3 x Flareon
1 x Dodrio
2 x Dragonair
4 x Dragonite

Trainers

1 x Professor Oak
2 x Bill
2 x Clefairy Doll
2 x Energy Removal
The strategy is to get his evolved pokemon and magmars out semi-quickly and attack the enemy to death. Remember this is a 5 year old's deck, not a 15 year old's.
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Overview

Since this is a younger person's deck, I'll try to cover and explain the basics in the fix. I'll be honest, though- the deck does need work. Everything's way too random and spread out.

Pok閙on

In a deck of sixty cards, if you wanted to draw a Charmander and evolve it to Charmeleon, the odds would be against you. The odds of getting both when you need them are pretty bad. This is why you want multiples. To have room for four Charmander and three Charmeleon, you need to take out other Pokemon families. I wouldn't go over 4 or 5 different families. You've got 11.

Let's start by taking out unneccesary Pokemon. The Dragonite family isn't very good and takes up a lot of room, so let's take them out. Charmeleon, Ninetales, and Arcanine is too redundant (3 families that do almost the same thing), so I'd just choose one of those and take out the other two. The best one in my opinion is probably Arcanine, so let's drop the other two.

Even though you've got several good families, you've got too many, so you'll need to choose certain ones to keep. Let's take out the Dodrio line, the Tauros, and the Moltres (he doesn't really fit the strategy, he's a staller). It's looking slimmer now, but I don't like to use more than two Evolution lines, so I'd take out Ponyta and Rapidash. You're now down to four families, two of which have evolutions.

The next step is to use the space freed to balance out the number of each Pokemon. Let's add three Growlithe and two Arcanine. Fossil Magmar is better, so make all three Fossil. Add another Kangaskhan too.

Trainers

Clefairy Doll doesn't really do anything, so why use it? Take those out and add another Professor Oak and two Bill. Energy Removal are good, so add two more and two Super Energy Removal. Let's add three Gust of Wind too so you can attack the Pokemon your opponent is building up on his bench. Add two Computer Search to get what you need when you need it. And since Arcanine and Flareon discard Fire Energy (Jungle Flareon, not GB... I'm not sure which you're using), add three Energy Retrieval.

Energy

You could use some Double Colorless for Kangaskhan, Flareon, and Arcanine. Take out one Fire and add four Double Colorless. Here it is: 
Pok閙on (18)
4 Growlithe
3 Arcanine
3 Eevee
3 Flareon
3 Magmar (Fossil)
2 Kangaskhan

Trainers (20)
2 Professor Oak
4 Bill
4 Energy Removal
2 Super Energy Removal
3 Gust of Wind
2 Com. Search
3 Energy Retrieval

Energy (22)
18 Fire
4 Double Colorless
It looks a lot different, but it will work a lot better. Try it out, and you'll see what I mean. Good luck! I don't know how much of this a five year old would grasp, but I tried... I'm hoping his brother will answer his questions.

~ Souper ~