One of the hardest things to handle for me-is being lonely-when I'm not alone. Which, I imagine would happen if I were in a situation where I was secret-because-even though my "love" is technically present, they may not be free to be physically present FOR ME.
One of the big things I would suggest, is spending some of that time with the kids-really nurturing loving relationship with them. It kind of sounds silly-writing it, but the closer they are to you, the more connected and family-like their relationship with you, the more affection they will freely give you-AND by nature, expect to be "normal amounts of affection" for you to have from their parents.
I have kids ranging in age from 5-21. Its very evident that the closer THEY feel to someone (anyone) the more THEY want that person to be close to us (their parents). Therefore, in coming out poly-one of the things that benefited us greatly in the end, was that the kids already had a close, meaningful and deeply affectionate relationship with my boyfriend-every single one of them. They all knew him as "part of the family".
The next thing I suggest is finding an activity that you really enjoy-without them-any of them. A weekly thing you can go do, make friends OF YOUR OWN that you can be yourself with and also get affection from.
Finally, it's never a bad thing for partners to brush up on "covert skills". Like leaving hidden love letters for you to find later, making a romantic cd for you with handpicked love songs that tell you how they feel about you (especially if they include something humorous); so you can listen to it when you can't get directly connected to them, sending flowers to your work secretly (the wife could take a card and buy them, send them-so no one starts thinking he's having an affair), picking out an outfit for you to wear and leaving it set out for you-with something special to make you think of them along with it...
If you are into kink and/or toys-I have suggestions along those lines too.
But, won't elaborate unless you inquire.
These are things my husband and I as well as my boyfriend and I do to keep the love and excitement alive. Even reading a book, underlining the parts that make you think of one another and then letting them read it, and see all those underlined "secrets".
"Love As Thou Wilt"