I thought enough of the 6.5mm that I bought one as a rifle for my daughter, then 11. Your thinking is good. The 6.5 is an ideal youth rifle. It's also one that can be used VERY well by adults. You won't necessarily out grow it. In my opinion its much more versatile than many others, like the .243 win.
There are a bunch of 6.5's out there. I opted for .260 in a Rem Seven Youth. I also spent a little time on ebay, and now I have three stocks for it. One is a regular youth stock, one is full sized, and one is a 'super youth"- I took a youth stock and cut an additional inch off of it. You really do want a rifle that fits. If the stock is too long, shooters tendto lean backwards to try to balance the rifle. THis accentuates recoil, making it seem worse. The stock HAS TO BE SHORT ENOUGH to fit the user. Likewise, the barrel has to be light enough to be held by those skinny little kid arms. Short is light. Beware though: Barrels less than 20" start to become VERY loud and muzzle blast can be intimidating. The little ruger compacts with 16" barrels are wickedly loud and this often scares the crap out of novices. I personally would opt for 18 to 20 inch barrels instead o a 16".
If you were to reload, the options are fully open. I do reload, and I have developed some 120 gr ballistictip loads at 2400 fps. Recoil is very mild. This load is an exact substitute (ballistically speaking) for the 6.5 JDJ cartridge, which has an excellent reputation as a deer killer amongst the TC Contender crowd. I also load 130 Accubonds to about 2650, which makes for fantastic whitetail and caribou loads. Reloading helps.
If you do not reload, I'd encourage you to think carefully. The 6.5 Creedmore is a great cartridge BUT 1) You aren't likely to get all that Creedmore accuracy out of a regular carbine, and 2) ammo is going to be scarce and expensive. You might find a .260 a better deal, and even it is scarce. I've got a cabinet full of odd caliber rifles - .218 Bee, .375 Winchester, etc. Let me tell you this: I am glad I reload. Those 375 Win are $44 per box of 20. I can load them for about $15. I suspect creedmore is going to be damned scarce and pricy too. 6.5 Grendel, 6.5 JDJ, 6.5 Creedmore, all of them are great, but none of them are commonly available, and all are $$$$. Reloading helps.
If the creedmore does end up looking too odd, I'd try .260. You aren't going to find 260 at walmart, but you will fnd two or three different 260 loads at most good gun shops. 6.5 creedmore is only loaded by Hornady and Nosler, and here are only about 6 or different 8 loads available. If hornady stops loading Creedmore, you are screwed. There will be no factory ammo available at any price. I don't know if you ever heard of calibers like 9mm Federal, .32 Remington, .303 Savage, 307 Winchester, 356 Winchester, and 41 Action Express, but there are boatloads of specialty calibers that were highly lauded in there day, and then quietly disappeared after a couple years. I fear Creedmore may well go this way. Grendel is a likely candidate too. How about .30 TC, .338 Marlin, and ,338 Ruger Compact Magnum? I doubt if you'll find these on shelves in 2020, and when you do find them, they will be 3times the price of regular common ammo.
On the other hand, there are some 20-25 different 260 rem loads available, loaded by a half dozen different makers. And one of those loads is a reduced recoil loading (no need to handload). In ten years creedmore might be available, or it might not. But 260 will still be on shelves, more widely available and at a more reasonable price. I'd have no hesitation opting for creedmore if I reloaded, but if I did not reload, I would buy the 260.
250 savage is a great starter too. However, its scarce and almost no rifles are made for it now. 257 Roberts is fantastic, but its the same as 250 for rifle availability. 7mm-08 is great and common, but recoil is increasing. 243 is very common, and very low recoil,but is limited by bullet selection and simply isn't as useful. in my opinion, the .260 is damned near perfect. It is ballistically identical to the creedmore (both toss 140's at 2700fps) and the 260 is solidly established and available. Its not as common as 243, but its a whole lot more common than the creedmore.
edit: The long range reputation of the creedmore is made with 24"or longer barrels. These aren't going t work with kids and their strengths. While published speeds are 2700 FPS with 140 grns, this is out of 24" barrels. You are going to be doing well to get 2600 out of a 20", and if you opt for 16" Ruger compact, you'll be lucky to see 2500 fps. Small skinny barrels on youth carbines are great for kids, but they aren't going to work as well "for longer ranges".