While the sites say you can use 10g leader, I'd not put them in anything less than a 15R or 20L. (15R is 3/4 the length of a 20L and same other dimentions, a very nice tank for modest but "bigger than a 10" fishkeeping)
You need precise and complete covering over the tank for Imbellis pairs as they tend to jump very accurately.
Keep in mind that "peaceful" in betta terms means "won't try to kill each other every second of the day". Imbellis have to be introduced to each other and you CAN actually have them decide not to get along. Not uncommon for people to have two or three pair in separate tanks. Some breeders may try to sell you Imbellis that also have some round-tail in them. Check the pictures for the wide color variation and the other traits. Remember that a roundtail male will kill a female then eat her while she's dying. Roundtails were bred for fighting.
Imbellis also need somewhat tighter water quality than Splendens, they prefer 6.1 to 7.0 which when combined with the hardness range becomes a bit trickier to maintain.
The following web site I've come to trust fairly well with its information on water stats.
I'd consider it a "no" for a child, they're not as hardy, no where near as cheap and require specific care.
Glo-fish are Danio and it isn't easy to kill them off. Do a fishless and make sure to spike it a few times to harden the biology.