To be honest, a lizard is not the best choice for a 5 year old or for someone who travels a lot, IMO, for several reasons. First, there is the issue of communicable diseases that lizards carry. Your child can get sick from handling a lizard if he doesn't consistently wash his hands. Also, you have to feed just about any adult lizard species at least every other day. You can go a few days if it is a very rare occasion, but certainly not frequently. You must feed babies not only every day, but some species must be fed several times a day. Then there is the matter of lighting, heat, and photo period. You could use a timer, but again, most lizard species must be fed at least every other day.
Are you aware of how big an iguana gets? Do you plan to accommodate an adult sized ig when it matures? Also, young igs are very skittish and bite and tail pop a lot, and your child could get hurt or he could injure the ig if it tries to escape and he holds on to it too hard. They are not easy pets because of their temperament, and they need to eat every day. They also must be housed properly with a proper temp gradient and access to UVB.
Beardies are also not easy pets to care for, especially babies. You cannot leave a baby beardie and not feed it for a few days or it will dehydrate and die. Beardies are expensive to set up, and don't need as much room as a green ig, but they are not small lizards as adults. To be humane, you will need at least a 75 long tank when it gets older, and both beardies and igs must have UVB, so there is another ongoing expense.
I am sorry to discourage you here, but I rescue and rehab these animals, and one of the prime reasons that lizards end up in my home is that people buy them for their kids without doing proper research, and it just doesn't work! I implore you to rethink getting a lizard for your five year old, or at least rethink these two particular species. IMO, they are just not appropriate for a small child.