We are going the last week of August. It is so hot during the day to do the parks and we are staying at CBR and I don't want to go in am, leave and go back in evening. It's just too much traveling back and forth. We have most of our adr's in the parks or close by, we were thinking of going early afternoon and riding a few rides, dinner and then staying a few more hours. Leaving the parks by 8:30pm ish. Has anyone every used this strategy? We will be using the bus for traveling, so only want to do it once a day. Our 3 children are aged 12, 12 and 6 years.
I admit I'm a bit confused OP. The title of your thread saying arriving at 3 or 4... but in here you are asking about arriving
early afternoon, doing some rides, having a dinner and staying a few more hours, leaving by 8:30. Um... the math doesn't add up at all. For starters, "early afternoon" would be 1 or 2, by 4:00 you're at late afternoon. Second, in order for "a few hours after supper" to happen, you'd have to be eating around 4:00 (allowing an hour for supper) - basically the time your title says you plan to arrive, which doesn't give any time for rides.
So...
If your plan is to arrive at 1 (early afternoon), spend the hours of 1-4 doing rides, eating from 4-5 during the highest risk of showers, and then going back out to hit some more rides. Then yes, with FP+ this is not a bad plan. I mean, you're going to be in the park during the absolutely hottest time of the day - but whatever. That doesn't bother some people. And you're going the least crowded week of all summer, so crowds won't be nearly as bad as they would be in say July. Just make sure that you watch the MSEP and Wishes one night.
But, if your plan is to arrive at 3 or even as late as 4, then no, it's an awful plan. By the time you have rain/ride shut downs, supper, you'll get your 3 FP rides done, and that's probably it. IMO that's a waste of money.
Your best bet is to get up, hit each park at RD and play till early afternoon, do a late lunch ADR (around 2:00) and then head back to your hotel. Also, you will not be able to arrive at AK at 3 or 4, since it closes at 5:00.