We booked with Monumental about 2 weeks out for a weekday in high summer. Man are we glad that we did! Chose Monumental over some of the other guide services because it looked to provide a smaller, more personal experience, and it was the right choice for our family of 5, including 3 kids 14, 11, 9.
Monumental Expeditions was great. They emailed us the day before to check in and provide waivers that we printed at our hotel (or we could have just completed when we showed up). Met them at a local put in / county(?) park. Park fee was included in the price of the trip, not sure if it is for every outfitter.
Brendan, Free, and even the owner, Adam were there to meet us and get us prepped for our morning half-day trip on the Arkansas through Browns Canyon. Gave us a detailed safety talk that made it clear that safety was the most important thing on this company's mind. As we were putting in, we skated past 3-4 other outfitters, all of which seemed to have an entire flotilla of boats, 6, 8...our group was 2 rafts, most of one taken up by our family.
Once we were on the river, it was clear Brendan knew exactly what he was doing and made us all feel very comfortable. He was fun and funny, setting our kids at ease, while also piloting the boat expertly, maintaining safety, and explaining the geology, history, rock formations and river conditions in the area. The measure of a good rafting trip (to me) is that everyone in our trip stayed in the boat - when the water feels like 50 degrees (on a cool, overcast day), that makes for a more enjoyable trip.
Because it was late summer (August 1), we knew even before we booked that the river would not be as high as it was earlier. Apparently it was really "big water" this spring. Most of the rapids we went through were Class II and III (maybe III+), but that was plenty of challenge for us, while still keeping it fun. I don't know if I'd want to take young kids through much higher water, although opinions may differ.
Definitely recommend Monumental Expeditions and would go with them again if in the area.