This is not a stupid question at all!
I am familiar with this subject as I used to go on very long horse rides and my knees are buggered.
There are three methods if you can’t really squat properly but for all three of them, always ensure that the slope of the ground runs away from you and you are not peeing on to a very hard surface that splashes everywhere:
A Hold on to the trunk of a tree, you are facing it, like you are giving it a hug. Step back and lower clothing but don’t lower it so that it is around your ankles, just to lower than your knees is fine, stick your bum in the air and aim your hips forward, legs apart, so you pee angled downwards.
Some expert wild wee people separate their inner labia with their fingers of one hand at this point (sorry for tmi) so the stream can be directed more easily, and pee as forwards as they can with slope taking the wee away. You need to get the flow right, not too fast and not to slow.
B Sit with your knees as though you are sitting on an imaginary chair with your back firmly leaning on an upright rock or tree trunk. Lower clothes. Pee backwards, so slightly leaning forwards, if that is not too confusing 😀, with floor sloping away from you. This position has the advantage of being able to survey the land around you more easily.
C Find a fallen log or rock and sit on it. Check for insects, adders, and spikey bits! 😀 Shuffle back with your bum. Shove clothing down to your lower thighs. Shuffle back some more so your bum is hanging over back of log, then pee as if you were on the loo.
HTH! Sorry for the rather graphic instructions but it helps to know the right techniques. I would advocate having a discreet practice by yourself before joining a group.
You can also buy trousers now that have covered zips that go from front button to back waist, that you can unzip to pee without exposing your backside. (They are not as difficult to use as they sound.) Other models have strategic flaps. You can also go commando in longer walking skirts or push underwear to one side and wear a long shirt underneath your trousers or skirt that covers your backside area. Strange though it sounds you can buy just shirt tails that are elasticated at the waist that serve this purpose or very wide or deep elasticated woven fabric “belts” that cover strategic areas 😀. Have a look on-line in outdoor adventure type shops,
In the absence of suitable undergrowth, women who can squat a little carry an umbrella and use that to dive behind and cover their rear end. Or they pee between two open car doors with a look out flanking the side view. Or carry one of those modern quick dry towels to wrap
around themselves for this purpose.
Joking aside I think it’s important to try and encourage women who want to spend time outdoors to do so without worry. And fears about weeing are what stops a lot of women trying, but organisers of guided walks will be conscious of this.
Op you might try a female only walk first to get used to it all? Good luck and enjoy the countryside! Don’t let a natural bodily function stop you!
If you can stop worrying about it, you usually find that the desire to pee goes away as you get in to a walking rhythm and of course you are slightly more dehydrated than usual when you walk long distances. It’s important to keep drinking though.
I advise wearing black on your bottom half to start with and bring an article of clothing like a light rain poncho to wrap around your waist too just in case! And have fun!