I have characters in a reasonably active guild and characters that I solo. I play the first on a PVP server and the latter on PVE.
I've found that being in a family guild is all about multitasking. (Even just being on a PVP server -- you're always looking behind you.) You can get into a repetitive motion grinding and keep up with gchat pretty easily but when it comes to complex thought or maintaining a lot of different information in your head at once, or even just being left alone for an hour or so, being in an active guild is the worst place to be.
On the other hand, while playing a character solo gives you ample room to stretch and breathe and go as slow or fast as you want, and you don't get those distracting "Who wants to heroic?" requests (or my least favorite: "You could switch characters and heal us."), you also don't get to accomplish group tasks without dreaded pugging.
My husband and brother usually refuse to guild their alts until a certain level -- sometimes even endgame level. This way, they keep their alt "secret" from the guild so they don't get distracted from leveling but can still put the alt in the guild when the character is ready for group activities. Since leveling doesn't offer much to a guild beyond the knowledge that a person is online -- and the ability to ask that person to relog to an 80 for one's own benefit -- and I guess conversation and relationship-building, too, then I think this is an excellent solution.
Have somewhere to escape to when you need escape; acknowledge it as just an escape (for example, I don't expect my Birdfall to ever rock raids); and keep your mains close to your guild heart (don't neglect them in favor of your solo characters, if you can help it).
The key is to keep a balance of guild time and personal time so that you don't get burnt out or lonely.