IMO It's unfortunate that Benadryl and doxylamine succinate have anticholinergic activity, otherwise they'd be fairly decent sleep meds. I just personally can't stand anticholinergics.
I think a lot of what people attribute to anticholinergics is really an antihistamine effect. Maybe it's just my own personal bias as I had made that mistake in the past, but since then I think I have tried enough drugs to get some sense of the differences.
The anticholinergic effects of the nortriptyline I'm on, for instance, give me dry mouth, difficulty urinating (I feel like an old man!) and constipation. It does have an overall "feeling" to it but nothing, in my opinion, compared to drugs that have antihistamine effects on the CNS.
That being said, I agree with you. Which is one of the reasons I make sure my doctor keeps me supplied with hydroxyzine instead, which is also a first-gen antihistamine capable of crossing the BBB, but with a much smaller anticholinergic profile than the others. Interestingly enough, it's approved as an anxiolytic (although I don't find much effectiveness from it).
I do have actual seasonal allergies, with the symptoms being limited to intense full-body itching. Benadryl never did anything for me so I got myself a prescription after finding a study demonstrating that it took 75 times as much histamine to generate itching with hydroxyzine over Benadryl! That's huge. And it helps unbelievably well.
I also deal with kidney stones and other pain sometimes, and hydroxyzine is great for potentiating narcotic painkillers.
Sorry to be so long winded, but I love hydroxyzine
If you're looking for a sedating antihistamine with the fewest anticholinergic effects, it's definitely the one to get, 50-100mg would be good, it's about as sedating as benadryl on a milligram by milligram basis, in my opinion. I'm not sure why it requires a prescription when Benadryl does not, but it's usually not hard to get a prescription for an antihistamine anyways
The only reason I don't use it regularly as a sleep med is the morning grogginess that seems to go hand in hand with all antihistamines when used as sleep aids.