If the liquids are meant for the children, in theory, they should be allowed through security. Of course, you don't have any recourse if the person screening you objects.
Tayd gave some entertaining ideas (the breastmilk one was especially creative, amusing even to this mom who nursed quite awhile). One I might add is to say it's for the younger child. Some TSA officers have objected to older children bringing liquids. The exemption is usually meant for babies so say it's his.
My oldest was allergic to everything but it didn't stop us from flying internationally. He was very allergic to both cow and soy milk (soy is an allergen and he reacted even worse to it than to regular formula). I used hypo-allergenic milk and that was all he could take for quite awhile. I'm mentioning this in case you want to try it out (perhaps discussing it with a ped first). It's expensive but if you can bring milk in powdered form, it's much easier for travel. Would your child drink it, if you can't find soy in powdered form??
Let's hope that the epi pens are not needed. Just mentioning that if you do use one, you have to give it to a F/A for disposal as they can't go in the normal trash (either the galley or lav trash-"bodily fluids").
You can bring a doctor's note for the creams but I recommend that you try to get them in smaller containers and/or buy travel sizes for your carry-on's. You can put any size (that fits) in your checked bags.
If it's any encouragement, my son outgrew all his allergies. Once in a very long while, he still gets some rash from something but he went on to eat anything and I was able to stop the special laundry soap, etc. The girls were put straight on to anti-allergen diets and delayed solids so we never found out about any allergies!
Good luck!