20 ga shotgun slug NO. This is a big deer with a tough hide and shots over 100 yds are very common.
The 30-06 or the 270 are great bou guns. If the recoil is to much I might sudgest the 308? It is a 30 cal bullet that does not have the kick of the -06.
Sounds like a great family reunion

You could have the young man practice a bit with reduced recoil 30-06, 270 Win, or 308 Win loads and then switch to premium ammo for the hunt.

Rifled slugs in a 20 gauge will kick about the same as the above reduced recoil rounds.

Welcome aboard stinky. 8)
You didn't mention whether or not you may buy a new rifle for him or not. If you were I might recommend A Browning A-bolt Micro-Hunter in 7mm-08. The stock and barrel are shorter for smaller frames. I bought my son one several years back and he really digs it. In fact I like using it also. The recoil isn't bad at all, and it will do the job for you/him. It's also a nice flat shooting round, and can be used for Deer and Elk also if you want. My son's first Elk was brought down with this set up.
There are other makes of rifles similar, usually called mountain rifles I think.
Anyway, good luck on the hunt.

My wife and daughter can handle the 308 with no problem. I think a 20 ga. kicks more than a 308. They both hunt and shoot with a .308 and 20ga. w/slugs.

my guide suggested that he could use his 243 as well. i wasn't really looking forward to buying another gun right now due to the expence of the hunt as well as the other must by items for the hunt. i have a 30-06 that may be small enough for him so i will try the managed recoil ammo. anyone have any suggestions on which managed recoil ammo they have had luck with
thanks again
stinky

Use Remington 30-06 Managed Recoil in 30-06 for practice (as I did with my sons) and switch to one of the following for hunting elk:

* Federal Premium Vital Shock 180-gr. High Energy 180-gr. Partitions at 2,890 fps.
* Winchester Supreme (Nosler) 180-gr. AccuBond at 2,750 fps.

P.S.:

If you chose the 243 Win. route, upgrading to a tough premium bullet is paramount. Within reason, choice of bullet and shot placement are far more important than caliber.

thanks a bunch guys. i think i am going to make it happen with the 30-06. just seems like it will make the most sense and i won't have to take another gun, just my bow and fly rod i plan on hunting with my bow first and then the rifle secondly.
thanks again
stinky

Does the young lads 20 gauge have a chocked barrel or cylinder bore.?

A slug should not be fired with a chocked barrel at any time and the recoil would be horendous.

I'd suggest the 270 win. when considering recoil, overall performance and years to come.

his 20ga actually has a rifled barrel, but looking around at ammo i was wondering why i cannot find any ballistics info on the federal fusion carts. anyone know where to find them. I found everything elese on their website but that