Sorry also to add to @Wahoohokie’s experience, that in our most recent trips this has been worse & worse. This year we’ve gone in May, July, August, September, October & November and we always stay along Harbor so use this entrance almost exclusively.
The only times we’ve had where the Harbor security line hasn’t been backed is when we go 45-60 minutes prior to park opening. Even this last trip we made a point of being 45 or more minutes early & there was still some sort of a line, but it did move pretty steadily & only took 20 min at most but was still a line. I would strongly suggest being an hour early. You’ll not only minimize the time it takes to get through security but be among the first to be lined up for park entry & often times they begin letting in 30 min early so you’ll really only have 20-30 min. wait & a much happier spot being within sight of the parks rather than the security tents!
To help get us there quicker, we usually skip eating bfast at the hotel (but instead pack it to go) & make sure we have everything laid out so everyone can just do a quick change. I also have us shower/bathe at night or during midday breaks so mornings are faster. Those shortcuts help get us there 60 min. early & then when we have the down time of waiting at the park entry gates, I like to use that time to help the kids get situated with their on-the-go breakfast/snack & a drink if we weren’t able to do that prior to leaving the hotel room/in security line. Also we do the first application of sunscreen & get pictures of everyone’s excited faces at the gates. I have also been known to do my daughter’s hair in the park entry line (one less thing to do before getting out the hotel room door). And then if there’s still time, I check our plan for the day, walk everyone through the first few steps so they know what we’ve got geared up to do first. All of this is far more enjoyable than that awfully slow-moving security line & totally worth it to hurry up at the hotel to be there early.
What’s been most frustrating for me in these recent trips (the ones from August on) is that anytime we’ve taken a midday break, we’ve come back to GIGANTIC lines to get back in weather we come back after a short break at 2-3pm or a longer/later one at 6/7pm. There’ve been more than 2 times when we’ve been 60 minutes from security to park entry and that is just ridiculous. On one recent trip, to avoid this hassle we took our kids to the lobby of the GCH and had them take naps in the stroller while in the lobby and DH & I relaxed on our phones for an hour-hour 1/2 (the baby was slightly uncooperative in napping with everyone else as he had already napped in the stroller in the parks, but luckily we were near the Mickey cartoons that play in the lobby so that kept him pretty well occupied).
If your kids need that midday break to be rested, I would still take it at the hotel, but know that you should keep your plans for the evening very flexible, if you have FPs to come back to, make sure you are arriving at the security line near the start of your FP window or be prepared to forfeit it/miss it entirely if you’re cutting it any closer than that. And be prepared again to have that wait. You could try to pack much lighter for the evening & have most of the party go through the no bag line & just send one person through the bag line & catch up with them in the Esplanade if that’s a feasible situation for your party. Now that DTD is within the security perimeter, they could even browse through World of Disney while waiting for the person going through the bag line.