That is not a small penis size, it is average. It might look small to you because of your height and the fact that a guy's cock always looks smaller to him than it really is.
I would think that you would be in good shape to have sex in just about any position except perhaps for really exotic ones or ones that require you to have a long reach just to reach the target. Spooning for example, where you are lying behind her and you are both on your sides can be frustrating with some women depending on their flexibility and size of their butts, because it is easy to pop out.
Even guys who are significantly bigger than you will pop out in cowgirl position now and then, especially with a new partner. That is just a matter of you and your partner figuring out just how long a stroke you can both take and still remain in the saddle.
Personally, unless the woman has a strong preference, I would go for some variant of missionary the first time. A lot of women like it because of the eye contact. Put a pillow under her butt to tilt her pelvis up to allow a little deeper penetration. If she doesn't find it uncomfortable, you can also get her to put one or both legs up over your arms or shoulders which shortens up her vagina still more. If you are worried about embarrassing yourself by slipping out, in missionary you will have her relatively "pinned down" so that you will pretty much have control over how long the strokes are, and you can really bear down on her mons with your pubic bone.
If you are so much taller than her that you wind up looking at the top of her head in standard missionary, you can put her on her back on the edge of the bed and stand facing her holding her legs up. You can lean in to her a bit and this position also allows you a better view of the action, so you can see how far you can come back without danger of your cock slipping out.
If you hook up with a gal with more experience than you, which will probably be the case, and she has a preference just go with it. She will know more about fucking than you do and will almost certainly have been with guys just about the same size.
