I'm sorry if I sound like a downer, but there is no chance that your gelcoat is just dried out or etc. where those cracks are. The gelcoat is definitely cracked. But, what I am interested in, is why? Now, gelcoat *can* just crack. If it was put on a bit thick or whatever. But that is a slightly unusual crack pattern, and I'm wondering if the glass beneath is also cracked (may be or may not be), and/or if something inside the trailer caused it. It's perfectly possible that it is simple gelcoat cracking.
You can cosmetically repair the cracks, presuming you have no underlying fiberglass issue (don't despair; if you did it would also be repairable). This is known as a gelcoat repair. You would grind the cracks out slightly (i.e. make the thin crack into a more gradual "valley") and then fill them in with gelcoat that you'd tinted to match (I can tell you more about this if you plan to go that way). Then you'd sand/polish until it's all flat and smooth and matching.
As to whether you want to repair the (overall) gelcoat, well, a shiny, new two-part paint
job is pretty sweet, but it costs in money or your labor or both. I say that because it would be a shame to put on a paint
job like that without removing windows
(and re-bedding them afterward), belly band, etc. These projects have a way of growing. And you would almost certainly have it painted professionally if you were to go that way (you need supplied air respirators and etc.).
Now you could do your own one-part paint
job (or roll and tip a two-parter), but for myself, I would just keep fixing up the gelcoat until it was time to take it to a paint shop.
Whichever way you go, you will want to repair those longitudinal cracks, because they would telegraph through any new paint.
Or, you can just keep using it as-is while you work through the rest of your list
Just know that gelcoat touch-up, while it does have it's artistry, is not rocket science. If you can follow instructions and do tidy work, you are more than halfway there.
If you were about to embark on the job, I might have a few comments to add to this, but it's a good primer. Don Casey writes some good DIY stuff for boats.
Gelcoat Scratch Repair by Don Casey
For example one point I would add is that before you tried to match, say, the green color, you should compound/buff an area to bring the color back up, *then* match the gelcoat color. You can mix up a batch without the catalyst, and then smear it right on the trailer to check the color (then wipe it off). Then you can go back and make the same color with catalyst for the actual repair.