If you have a sitter make sure they will be tripping too. I dont like being around people I know that arent tripping when I am. Like my wife, she wont do shrooms anymore, but if I am or me and a bud are she usually goes to bed after an hour or 2, shit starts to get too weird and she cant really communicate with us anymore anyway.
I tend to agree with what you've said. If I'm tripping hard on mushrooms, and I'm around anybody sober, I tend to view them differently. It's as if we're alienated from each other in a way the other person can't possibly understand (and really, they can't). It doesn't make a trip bad, it's just an odd feeling... hard to describe really unless you've experienced it before.
I don't know if I'd necessarily recommend walking through the woods by yourself if it's your first time tripping. While nature is incredible on shrooms, you don't know how the shrooms are going to affect you. That could mean bad news if you're out in the wild and really start tripping hard (could get lost, possibly hurt yourself, any number of things really). If you do decide to go into the woods, take someone with you (or if you absolutely must go by yourself, leave a note telling people where you went or let someone know where you're going. That way if anything happens people will know where to look for you).
I recommend you trip somewhere safe for your first time. Preferably in an isolated house somewhere. You'll probably be okay if you're by yourself in this situation, but it never hurts to have someone around. One advantage of having someone else with you tripping, is that you'll both probably laugh your asses off (maniacally). If the other person isn't tripping, at least make sure they're someone you know and trust. You don't want those weird feelings I described associated with someone you aren't totally comfortable with. Set up something to play music on before you start tripping. Set it up so all you have to do is hit play; trust me, it'll make things a lot easier for you. Also, have some liquid ready. Bottled water, orange juice, something like that. Mushrooms often wreak havoc on my body temperature, and sometimes I'll literally be raining sweat while tripping, so don't be alarmed if that happens to you. And last but not least, make sure you have some place comfortable to sit/lay/etc. Some of the best moments I've ever had on mushrooms were getting lost in a couch or a bed.
Hope this helps.