Lots of seedlings.... too soon?

Last year my first set of tomato and pepper seedlings did poorly due to the off brand potting soil I used.
I did a second planting in early May and ended up with a great harvest despite the setback, but I was frustrated by the extra money and energy I had to expend.
This spring I was determined to do better. I bought premium potting soil and new seeds, a mat for bottom heat, and built new shelving to keep the light bulbs closer to the growing young plants.
But I didn't adjust my seed starting schedule to the late spring we've had, and now I have too many big tomato seedlings too soon. They have already been replanted into individual pots (deeper to get more root growth along the buried stem), and they continue to grow apace-- well, actually at too much of a pace!
Here's a pic (yes, there are some Moonflowers too):

So now the challenge is to keep them happy until the last frost, about a month away. I'm going to pinch the leader back on a few seedings to see if I can encourage branching, and I will also start to keep them at cooler temperatures. Finally, I will build a cold frame for them in the garden that will be insulated enough to take some of the bigger plants out for hardening off quite early, by the end of next week.  Just in case I lose some I did start a few more seeds this week.  Maybe next year I'll finally get the timing just right.