We traveled on the Pride in November and had a great time.I will tell you the boat had ALOT of motion in seemingly calm seas so just be prepared if that bothers you.It sure bothered my husband.
In Belize we did a ship tour -the river ride and ruins tour-we had our 10 and 12 year old with us and my parents-it was a very interesting trip and everyone enjoyed it-alot of people on the ship did the cave tubing and loved it.
There is not much of anything in Progresso-we went to Merida on a less than luxurious bus and did not enjoy the city-there is alot of great old architecture but the people in the city were VERY pushy,There is a small market in Progresso where the ship shuttle leaves you off.The people here were quite friendly.You can also walk the streets or just lounge on the beach although after Cozumel the water is disappointing.There is a Corona store were you can buy bottles for $1 and wear them around you neck.
Hope this helps and hope you have a great time
Wendy
