Need ideas as to "how" to get packed lunches/dinners to withstand 100+ degree...

We live in south Florida so heat is a familiar thing!

Yes, use an insulated bag. Put a freezer pack in the bottom and a second one on top of your food. 

Yes, RTD shakes will hold up but you do NOT want to drink these at room temp or warm. Yeccchhhhh. 

The one thing I'd avoid, though, is mayo based foods like tuna salad w/ mayo, etc. No need to tempt fate! 

The big ice blocks are great idea, we use them on car trips in ice boxes all the time. I also have some of the smaller ones to "top off the ice chest." They are able to slip down and fill in gaps to keep stuff cold all over. We do the chests a lot with road trips and drinks. And as you can guess whenever we open it, it lets warm air in. So we do the "layer" the ice I guess you could call it, to KEEP ALL cold enough. Just an idea to go along with the other good suggestions.

So I went to a robotics competition and had my snack/lunch packed and in the car with three ice packs in a thermal lunch bag.  When I came out for my snack (a yogurt) it was warm - ew!  Maybe something a little more substantial like a cooler would work better.  The ice packs were warm too.  I think if the car is sitting in the sun it just gets so hot that it works overtime melting the packs.

I had RNY and also worked security at minor league baseball games.  No outside food or drink (except 20 oz of clear liquid) was allowed in the stadium...I was in charge of checking people's bags.  People would walk up to me and say..."I just had gastric bypass, I need this to help me maintain my health".  I would have to tell them "sorry...Not allowed".  In my mind I always felt this was discrimination, but had to follow the bosses orders... 

Go to Target and purchase a cooler - just a regular cooler in which ever size you desire.  Fill with food and lots of ice.  Really not that difficult and leave in car for later consumption!

I do this all the time while wintering in Florida or while visiting in the summer when the heat and humidity is high- and I am often gone all day.  no problems

You don't need a Yeti, but invest $50-100 in a good cooler. A thermal lunch bag just doesn't cut it. It's not like you can't use the cooler for other events in your life, they last for a long time if you take care of them.

You can get a cooler that plugs into your car cigarette lighter.  My parents have one, I think they got it from LL Bean but I have seen them at other places.  It is basically a refridgerator.  It works really really well, if this is a regular thing it might be nice to have, and it doesn't need any ice which is kindof nifty.  I also have a hydro flask, it is an insulated water bottle, $20 or so.  It keeps things cold or hot for a really long time.  I haven't used it for a protein shake but I bet it would work well, especially if you but some ice cubes in it.  Congrats on your skating!

I sometimes freeze bottles of water and use them as ice packs and then later you have pretty cold water to drink too.