I just did your Delhi-Jaipur-Agra itinerary earlier this month. I think that you should have an enjoyable time. Know that your drive time between Delhi-Jaipur is about 5 1/2 hours, Jaipur-Agra about 4 1/2-5, and Agra to Delhi about 4 - 4 1/2.

Your tour guide at each of the cities will end up taking you to an overpriced store to try to get you to buy carpets, jewelry, marble, precious stones. You don't have to buy anything (although you will have to endure a guilt trip---ignore it.) Focus on the scenery and architecture and have a great time. Ask your guides anything. My experience was that their English is often not too good, but they know everything about the sites they are explaining. Every site in those places has a fascinating history behind it.

One thing, the guides will not do anything to prevent or chase off beggars. Walk fast and be steadfast. Get used to getting the soundtrack 'No' going. Be advised that some of them get quite nasty if you don't give them anything. Some even throw things (rocks, elephant dung). If you do give to them, however, prepare to be swarmed by others who appear out of the woodwork. Best advice is to ignore them and give to an Indian charity of your choosing, and not encourage that habit.