I feel like I can't be barefoot around him because every time I'm in the same room as him without my shoes on, he'll find some excuse to sit next to me and he'll start to tickle my feet. He isn't disobedient, so I can tell him to stop and he stops but the very next day he tries to tickle me again. Just last summer we were at the pool and I noticed he sat next to me while I was dangling my bare feet in the water and he began to tickle my feet while I was talking with my friend! Also, every time i sit in the recliner with my feet up, he will come and grab my ankle and tickle my foot for a long time until I can get it loose. I'm very ticklish, and this is inappropriate. How can I tell my son not to tickle my feet without upsetting or otherwise embarrassing him?
Articulate and enforce personal boundaries. Make it clear to your son that tickling your feet is not something that you are okay with, ever. When he does it, instead of telling him to stop, remind him it simply isn't okay, and impose consequences if necessary, as this kind of boundary violation will be much more significant later on in life. This approach would probably also work on your daughter's poking of your belly button.