Basic seedling pads raise the temperature 10-15 degrees over ambient. I use several (the cheapest I could find) in the greenhouse. Over the years, I have used them for Cattleya, Paphiopedilum, Vandas and most recently, Cymbidium.
If you are concerned about 'cooking' the seedlings, place them in bins with a couple of inches of water in the bottom. You can find my instructions on how to do this setup here:
Fair Orchids
Download the file named 'FO, growing orchid seedlings from flask'
You can use the same bins prior to deflasking.