You do not need to know the birthday child well to get this right. You need something dinosaur-shaped, inexpensive, and picked by your own child.
A small dinosaur figure, a dinosaur-themed activity pad, or a fossil-dig kit are all safe, inexpensive, on-theme choices that do not require knowing the birthday child's specific taste — the theme itself is the guide.
A drawing of a dinosaur, made by the guest, costs nothing and is very often the thing kept longest from the whole party — birthday gifts get absorbed into a toy box; a handmade card from a friend does not.
"Anything specific they would love, or is a themed surprise fine?" is a normal question to ask and saves everyone guessing. Most hosts are glad to be asked.
Yes, and often underrated — a dinosaur book with real photographs works at almost any age within the theme.
Take that seriously — it usually means exactly what it says. A card from your child is still a nice thing to bring regardless.
Part of our guide to Gifts for one obsession.