Jajone, it was pretty easy. I ended up getting some pinking shears (cheap JoAnn ones with a 40% coupon) after I was done and going back over the seams with it. Also try and get thin interfacing. The stuff I got was kind of thick but, I was in a hurry when I got it and wasn't thinking. Next time I will get the thinest I can find. Otherwise it is easy to sew. I am a beginner too. I did not do the snap crotch but, you may want to at his age.
My Ds was wearing 18 mos at 1 year too. I would say if your Ds is usually in the larger percentile height wise you will be fine. If it ends up being a little big you could always take it in a little. My Ds is 21 mos now and the size 4 fits him perfectly he is always in the 98-99% on height.
I think I would make a mess of the snap crotch. I thought about skipping the buttons on the top as well and just putting velcro and a button for looks. It looks easy to get on and off without the snaps.
Finally, I'm done, and I can sew the pants together. Keep in mind that I have twins so I appliqued 10 of the Wiggles guys. There will be ruffles on the ankles in the same fabric as the music notes.
I'll be starting on appliqueing the second shirt as soon as I get the pants finished.
Like I said earlier, I could sell an outfit for $1,000 and still feel like it wasn't worth the money. I've been working daily for 3 weeks now, and I'm still a few weeks away from being done.
I posted a close up pic a few pages back. I am so not artistic that I am really impressed with myself.I'll never be as good as some of the ladies on here, but I'm just glad I made something that doesn't look half bad 