@media (max-width: 950px) {
	#branding,.header-link {
		min-height: 80px;
	}
}

@media (max-width: 980px) {
	#branding,.header-link {
		min-height: 60px;
	}
}

Remove those lines from your custom CSS and the larger custom header image should go back to being large on an iPad. Or, if you want to adjust the header differently for an iPad, then keep the @media rules but change the CSS inside them to make the header image look how you want. Note that you can make your computer browser window smaller than 980 or 950px to test.