First of all, pat yourself on the back that you have completed those tops. And welcome to the UFO group. lol
What patterns did you make? Do they have nice straight lines where you could do SID (Stitch in the ditch)? That would be my recommendation for you. Try SID. It is the method I use most, because I am still afraid of FMQing.
My first quilt that got SID'd was full of little puckers, because that was the best I could do at the time. The recipient loved it and still uses it. Nobody noticed the puckers. I still have trouble staying right in the ditch, so I renamed the stitch to MAD (Meandering around ditch)
So what is the worst that could happen? Common, you can do it. The key is do keep the sandwich taught and baste thoroughly. THere are some nice Youtube tutorials online to help show how to sandwich, what to consider when basting, how to pin......
My machine has a special foot for SID and that helped, but it is not necessary.
Now, if you have the money, you could find someone who rents Long-arm time and you can quilt it yourself on a longarm quilting machine. That eliminates a lot of the prep work. You just have to make sure that the batting and backing is large enough.
If you mess up, you can pick the stitches and start over - but I bet you'll do just fine.