April was supposed to be 75 in TAS. Memory Alpha places his birth at 2195, meaning he'd currently be 61 on Discovery. So, yeah, Shatner's definitely too old to play him.
Kirk died. Shatner wanted that to happen. Also the last time he flirted with a Star Trek TV guest appearance - on Enterprise - his ego wanted a ridiculous amount of money. He should stick to making documentaries about himself. They're pretty funny.
However, Shatner looks somewhat younger than his actual age, perhaps due to certain medical interventions that are readily available to stars of his stature. Kor
Shatner keeps wanted to have a change of heart regarding Kirk's fate but 20 years not long enough for that. Dumb Shatner
AFAIK, it was not about money, it was them wanting him to play a character that was not Kirk. Which, as noted, is a stupid idea.
If Shatner plays april can you imagine the chaos amongst fandom? People will debate why april looks like Kirk, is April really Kirk's father? In 30 years writers of another star trek series will be compelled to write a 3 episode arc, which explains how Kirk went back in time but forgot his wallet and had to donate to a sperm bank for some quick credits. Kirk's boys are later used by April's mother hence why april looks like kirk.
I would assume he was a well seasoned Captain when the Enterprise launched in 2245. If we go by TAS, which stated April was 75 in 2270, April would be 61 at the time Discovery takes place.
As much as I like the Shat and Captain Kirk. It makes zero sense to have an older Kirk appear played by Shatner. At best, in the current time period, Kirk is a brash up-and-coming junior officer...probably a Lieutenant somewhere. (possibly a Lt. Commander...since he's a rising star.) Nobody in the current time would know (other than his current crew mates/friends etc) who the frak 'old Kirk' from the future (if that's how they use a Shat guest shot) even is. They certainly wouldn't know he's some famous captain from the future...as that he not famous in this time period yet. And besides all that...'old Kirk' is 'dead' in the Prime timeline from what? 2290's to 2370's...and then he's really dead...so just how do you have and even older Kirk show up anyway? Fan Wank, nothing more.
We know George Kirk was in Starfleet and should still be alive, though he is probably around 50 at this point. Do we know anything about Kirk's grandfather's? Were either of them in Starfleet?
That's not even the worst idea I've ever heard. I mean, if you must stick a Kirk in Discovery somewhere.
Tiberius was going to have been a United Earth Stellar Navy officer in the Star Trek: Beginnings movie that got cancelled, a Romulan War vet.
As as I'm concerned, it'd be cool to have Shatner participation on some level - virtual hologram cgi type of seal, voice communication or log, etc. Fan wank happens all the time. Being Discovery is set within TOS' time period, I think it would be a great thing to do. Honor the men and women from TOS who started this whole thing. And why not Kirk - one of the Federation's greatest heroes?