I honestly don't know if all were booked as CLFP -- the reason being that we didn't happen to try to modify any of them until the we hit the 6th FP on Day 3 of our trip. I recall noticing that I wasn't able to modify our last one on Day 3 and thought it was strange, but that I must have been confused about which ones were the CL ones and which ones were the regular ones. It wasn't until the morning of Day 4, when my H didn't feel well and we were trying to move passes to accommodate for his illness, that we discovered that indeed our regular FP had been booked as CL ones (and we know this because this time we checked the spreadsheet we'd made confirming that the regular FP were supposed to be the first 3 that day, and we also confirmed it with both our CL CMs and DSS).
To be honest, whether I'd be willing to use that workaround again would depend entirely on the kind of trip we were going on and the time of year. If it were just a low key trip with me and my H, and it wasn't a super busy time of year, we would skip the CLFP. But if it were Christmas week again (or some other crazy busy time like that) and/or our D was with us (and she's all about the rides), I would still book them and try to get DSS to use that workaround because for us it would be better to have them and not be able to modify ourselves than it would be to not have them at all.
In your situation, I would take into account the time of year of your trip, as well as the ages of your grandsons, and whether you all plan to ride everything together. If there are some members of your party who don't meet the height requirement for some of the E-ticket type rides, or who don't wish to ride, but you all want agree to only do rides you can all go on together, you may find you don't need the CLFP. Also I would consider perhaps only buying the CLFP for certain days and/or parks if that would help you get under the FP limit. For example, because there are no tiers at MK, I personally think that except for the busiest of days that the CLPF aren't as necessary. But for a park like HS, where they have just redone the tier structure and made almost every "ride" a Tier 1, or for AK, where Pandora FPs are still pretty hard to get, the CLFP can be a huge advantage. For me, I think you could argue either way with EP...Frozen, Soarin, and Test Track are all considered Tier 1, so the only way to be guaranteed to get all 3 in one day is by buying the CLFP...but then again, we are usually able to obtain Soarin and Test Track (and sometimes Frozen) as a 4th regular FP just by being persistent about refreshing. YMMV of course.
Hopefully I have given you some ideas to think about. Feel free to ask me any other questions, and I'll try my best to answer them.