Given your goal, read this thread
front to back. You will get the results you are looking for .... guaranteed.
JMHO. I wouldn't stock 5000 4"-5" CNBG in your pond this spring. Did he tell you why so many of that size? What did say attempting to gain your confidence in that approach? What else was recommended to support this action? Some people are smooth talkers and are experts at gaining confidence and making sales. I would tread carefully because something tells me you will be disappointed in the return of this investment ... even while he's totally satisfied. When it doesn't work, and it probably won't, there will be plenty more recs, probably as costly as this one.
You mention that you just want to take your grandkids fishing and catch some decent sized bass. Take them fishing, I guarantee you that they will enjoy the fish that are there. Grow the bigger bass for yourself and they will enjoy them too, but they don't need bigger bass to have a great time right now. So take them fishing, harvest the LMB appropriately and have some shore lunches. What great memories you will make for your grandkids and yourself. Whatever, you would have spent on CNBG, I would spend that money on making a nice area for relaxing at and cooking your shore lunches. If you have money left over, think about fertilization and/or feeding but only if you think you don't have enough fish in that 5 acre pond. I mean, 5 acres will probably produce more fish than you want to harvest just as it is. Why compound the problem of too many fish with way too many fish?
Bocomo's thread is a text book example of how to transform and old pond like yours through fishing and harvest. I can understand if you are willing to fork out the bucks to start over and have a much better pond for a few years in just a couple years. After all, it's just money. But your post seems to be asking do you really need to spend $7500 right now to have bigger bass. The answer is no, you don't. In fact this rec will not help you unless you spend a lot more money fertilizing and enhancing carrying capacity. It's just money and if it gives you what you want then it's money well spent. It's just that some tells me that this isn't the best path for you and the return of this expense won't be satisfying.