If the scope is the 70mm identified by Sonny, I recommend getting him a better eyepiece. The scope comes with one that is about 26mm and one that is 8mm to get the 78X power. That higher power eyepiece is basically too high a power for that scope and the barlow on top of that makes it even worse.
When I got my first scope, it came with two eyepieces. The one for the higher power was essentially worthless and I never bothered using it. And it had a Barlow lens too, and that only made things worse. Telescopes have a maximum useful magnification value and if the optics were perfect, and the seeing conditions were perfect, that would be approx. 50X per inch of objective. Both of these are not likely to be met, and a more realistic figure is probably less than 25X per inch of objective which at 70mm (2 3/4 ") which would be 68X (which is less than what is being supplied). Thus, that high power eyepiece is not likely to be used much since the image will basically look awful.
So I too had that problem. So I got the Edmond Scientific Catalog and ordered a 28mm 1.25" barrel Kellner eyepiece for $7 (that's dating myself).
What I found was that this eyepiece was absolutely superior in every way to the supplied eyepieces I had and made that scope so much better to use. This eyepiece also had a much wider field of view which made it so much nicer to look thru also. The stock lower power eyepiece was similar in focal length to what I had, but the field of view was so narrow that it just wasn't fun to look at anything. Sort of like looking at the world thru a straw (although I am exaggerating a bit).
I still have that old 28mm Kellner lens and today, I use it on a finder scope. Much better than the eyepiece that came with the finder scope.
As for what eyepieces I use now, I have a set of Baader Hyperion eyepieces with 68 degree field of view. I don't recommend these for a 7 year old, but the cheap Kellner I used would be perfect.
By the way, Kellner is the lens design, not the lens manufacturer. There are a number of different lens designs with some designs costing a lot. Kellner is a very simple, and very cheap design, but not as cheap as what they ship as standard eyepieces.
I will finish with a quote from this link regarding Kellner lenses: (My old Kellner doesn't even have a brand name on it and it sure works great. The lens opening is very wide, more than 1 inch, and the eye relief is great)
http://www.cloudynights.com/page/articles/cat/articles/how-to/eyepiece-review-pitfalls-r361Eyepiece Designs
Over the years a number of different eyepieces have been designed. They are usually named after the designer, which is why you always see the name capitalized. [FOV]
Kellner (Ke or K) [40] Designed when f/6 was a "fast" scope and is better with f/6 or slower scopes. I accidentally put a Kellner in my f/10 telescope one night when I was viewing a star cluster. To my surprise I could see more stars and the whole scene was brighter. Now I use modern Kellners whenever I am viewing faint objects. Dont bother reviewing a Kellner in a f4 scope though.
The Rank Kellner (RK) [45] was designed a bit later when scopes were a bit faster. The RKE is a later RK and uses a special glass element to provide a better wider view with even faster scopes (but not much). For some telescopes on many objects on most nights the RKE provides as good a view as many folks want.
I have found great variation in the quality of Kellners. In general newer, fully coated, K, RK and RKE are the best. Older Kellners, especially Orion brand are of less quality.
Just wanted to add that I found out some information on my old Kellner.
http://www.astronomyforum.net/telescope-eyepieces-forum/140513-edmund-scientific-rke.htmlAnd even found a picture of it:
http://www.surplusshed.com/pages/item/l13596.htmlAnd this is what they have replaced it with: (Plossl is a newer design that is superior to the Kellner)
https://www.scientificsonline.com/product/scientifics-plossl-eyepieces-f28mm-3082255?gclid=CIee8e6zqskCFdc2gQodewAL7A?gclid=CIee8e6zqskCFdc2gQodewAL7A