Some of the better regionals can pay $100K after ten years or so, even sooner if you volunteer to be a check airman.
At age 35 you need to consider...
1) Do I already have any retirement plans in place? If not you might want to focus on that before a career change.
2) Do you have a college degree? If not, that will make it significantly harder to get a major airline job.
3) Family/kids: Do you have them? That will greatly complicate things unless your wife has a high-paying job that is PORTABLE on short notice (ie specialty nurse, MD, or something like that).
4) Are you in better-than-average health? Entry-level regional airline flying is often grueling and can wear down a 24 year old...but he will bounce back after a good night's sleep. Will you?
5) Age 65: The age 60 rule will almost certainly change to age 65 in the next 2-3 years...this will do two things:
a) Slow hiring at all levels for several years in the near future.
b) Give you an extra 5 years to work...but ONLY if you stay in exceptionally good health: Good diet, DAILY exercise, low body fat, minimal booze.
6) If you end up staying at a regional, you probably want to have a back-up career so that you can make money on the side or in case your regional shuts down. Do you have skills you can fall back on?
7) Loans: How are you going to pay for training? If you take out school loans, you will be paying them off for 10-15 years...
As far as ATP goes, all of the big-name "Glossy Brochure" flight schools offer the same training that you can get at your local school, but they do it assembly-line fashion. The training is not going to be better at all with one possible exception: Classroom training. If a school's classroom instructors are low-time cfi's the training will probably be pretty basic...this is typical of small and large schools. If a school uses experienced professionals (off-duty airline pilots, retired airline/military, etc) then the ground schools might be better. But how much is that worth?
The best plan is a small school at your home airport...that way you don't have to move and can hopefully keep your day job until you have the ratings to get a full-time flying job. If that's not an option, I think ATP is the most reasonable out of the big schools.